What is disk write speed. Types of computer memory

What is speed CD-R recording.

The term "write speed" defines how quickly data can be written to CD-R disc... Marking 2x, 4x, 6x, 8x, 12x, 16x, 20x, 24x, 32x, 40x, 48x shows how many times faster device writes data compared to a single speed reference. One speed is understood as a data transfer rate equal to 150 Kb / s. Thus, the marking "2x" means that data can be written at a speed of 300 Kb / s, respectively "8x" - 1.2 Mb / s, and "16x" - 2.4 Mb / s. It must be taken into account that real speed may differ depending on the selected recording format, since data is written in 2 "mode, 048 bytes per block, and sound information- in mode 2 "352 bytes per block.

So real time recording one full disk may differ slightly depending on the format. Usually marking CD-ROM drives consists of one number, reflecting with what maximum speed data can be read. In this case, the fastest format for reading is indicated - CD-ROM Mode 1, moreover, moreover, when measured on the outer perimeter of the disk. CD recorders are marked with three digits: the first is the write speed CD-R discs, the second is the rewriting speed (CD-RW discs), the third is the reading speed. Accordingly, marking 16x10x40 for a CD recorder means that it is capable of recording CD-R discs at 2.4 Mb / s, CD-RW discs at 1.5 Mb / s, and reading discs at 6 Mb / s. If the marking consists of two numbers, it means that such a drive cannot work with CD-RW discs.

Disc recording modes:

disc-at-once (DAO) disc burning:

This is a recording mode when a disc is recorded immediately from beginning to end, without interruptions. Those. the laser beam turns on at the beginning of the disc recording, and turns off only at the end of the recording. First, the disc is written special information, marking the beginning of the recording (lead-in), then the data itself, and at the end the final information (lead-out). Generally, the DAO method is preferred if in further drive will be transferred to the factory for replication, and the recordable CD-R is the master disc. Recording in DAO mode allows you to avoid bundles of input (run-in) and output (run-out) blocks, which are associated with multisession recording by mastering equipment and make the disc unsuitable for making a matrix from which cd replication will be performed.

track-at-once disc burning (TAO):

The TAO recording mode allows you to record a disc not immediately from beginning to end, but in several passes: initially you can write one sound track(track), then another, and so on. Accordingly, how many tracks are recorded on the disc, how many times when recording laser ray will turn on and off. Laser on / off is perceived sound players like a 2 second pause between tracks. It should be noted that an audio disc recorded in this way can only be read on a regular CD player after the table of content (TOC) has been written. After TOC has been recorded, it is not possible to add tracks to the disc.

session-at-once disk write (SAO):

SAO recording mode is usually used when recording the CD-Extra format - a format that combines the audio part on a disc (CD-DA format) and software part(CD-ROM format). When recording in SAO mode, the laser beam turns on at the beginning of recording the audio part, turns off at the end of recording tracks, then turns on at the beginning of recording a part of data and turns off at the end of the recording. The TAO mode is also applicable for preparing CD-Extra format discs. In this case, during the recording of the audio part, the laser will be turned on / off as many times as there are tracks on the disc.

multisession recording mode

Ultisession is a recording mode that allows you to add a CD, that is, add new information to the previously recorded. Each session contains a record of the beginning of the session (lead-in), then the data itself and the final information about the session (lead-out). Unlike disc-at-once recording or injection-molded CD, there can be up to 99 such sessions on one disc. When recording in multisession mode, structure information previous entries copied to the new session and can be fixed. Thus, when recording in multisession mode, the user can destroy information about the structure of already unnecessary or obsolete records without including it in new table content (TOC - table of content). This means that it becomes possible to "erase" unnecessary information from the CD, although in fact, it physically continues to remain on the disk and can be restored using a special software... The disadvantage of the multisession mode is that disk space is wasted, since it separates one session from another. About 13.5 MB is lost each time (6 "750 blocks). The more sessions recorded on the disc, the more space is wasted for the session separators. In addition, some older CD-ROMs (usually released before 1994) cannot read multisession discs. hence

I am writing live data to a blank spinning disk sequentially. (EDIT: It doesn't have to be sequential if I can read it as if it were sequential.) Data comes in at 100MB / s and the drives have an average write speed of 120MB / s.

Sometimes (especially when free space starts to decrease) the disk speed is less than 100MB / s depending on where on the disk the disk is being written to and I have to throw important data.

Is there a way to write to disk in a template (or some other way) to ensure constant speed recording close to average speed? No matter how much data is on this moment available on disk.

Some comments on why I think this should be possible.

When normally written to a disc, it starts from the fast part of the disc and then writes to the slower side. However, if I could write half the data to the fast part and half the data to the slow part (i.e. in 1 second it could write 50 MB to the fast part and 50 MB to the slow part), they should meet in the middle. Could I achieve constant speed?

As a programmer, I'm not sure how I can work out where on the platter the data is written or even if the OS can achieve something similar.

6 replies

Divide the disc into two equal sizes. Write a few seconds of data alternating between sections. This way you get almost all the usual serial speed well averaged. One disk searches every few seconds almost does not eat up. One request per second reduces the usage time from 1000ms to ~ 990ms, which reduces the throughput by 1%. The more RAM you can allocate for buffering, the less you need to search.

Use more sections to increase the averaging effect.

If I had to do it in conventional system Windows, I would use a device with a higher average write speed to give me more possibilities for storage. The expected 100MB / s average write speed across the entire disk, calculated at 120MB / s, is going to get you in trouble. Spinning hard drives does not have a constant write speed to the entire disc.

The usual solution to this problem is to buffer in RAM to cover infrequent slowdowns. The more RAM you use as a buffer, the longer you can deal with the slowness. These are the trade-offs that you must make. If your problem is a known slowdown in the inner sectors of a spinning disk, then your device is simply not fast enough.

Another thing that can help is to access the disk as quickly as possible and secure it sharing other parts of the system. Use a separate physical device, don't format it with the filesystem, don't write directly to the shared space. Yes, you have to deal with some of the problems that the filesystem solves for you, but you're also missing out on a bunch of code that you have no control over. Even then, your application might encounter scheduling issues on Windows. Windows is not an RTOS, there are no guarantees regarding the timing. Again, this will help a lot more with temporary slowdowns from cleaning up the filesystem, cleaning up dirty pages, etc. It probably won't help with the "latest 100GB write problem at 80MB / s".

If you are really stuck with a drive that goes from 120MB / s -> 80MB / s outside the home (you have to test your own code and not trust the specs from production so you know you are dealing) then you have to play split games as others have suggested. On a mechanical drive, this will lead to a serious head search that can eat up your enhancement. To keep requests to a minimum, it would be even more important to provide it with a dedicated disk that the OS doesn't use for anything else. Also, use large buffers and write many megabytes at a time before looking to the end of the disk. Instead of partitioning, you can write directly to the block device and control which blocks you write behind. I don't know how to do this on Windows.

To fix this problem on Linux, I would be tempted to test mdadm raid0 on two partitions on the same disk and see if that works. If so, then the work is done and you don't need to write and check complex mechanism records.

I am afraid it might be harder than you realize:

• If your average write speed of 120MB / s is the manufacturer's value, then this is most likely "optimistic" at best.
• Even the reference write speed is usually done on a partitionless / formatted disk and will be faster than what you usually see in actual use (how much higher is a good question).
• More important is minimum speed records. For example, from Tom Hardware 2013 HDD Benchmarks, a drive with an average of 120 MB / s has a minimum of 76 MB / s.
• A drive that is being used by other applications at the same time (eg Windows) will have a significantly slower write speed.
• More greater importance has the actual measured performance of the drives. I would make a simple application similar to your use case that writes data to disk as fast as possible until it fills the disk. Do this a few (ten) times to get a more realistic average / minimum / maximum write speed ... it will probably be lower than you expected.
• As you noted, even if your "real" average write speed is above 100MB / s, you run into problems if you run slow speed write just before the disk is full, unless you have somewhere else to write the data. Using a buffer does not help in this case.
• I'm not sure if you can actually specify the physical location to write to HDD these days without going into the drive's firmware. Even if you could do it, my last choice for solutions.

A few specific things that I would like to address your problem on:

First of all, I hope you are using raw disks and not the filesystem. If you are using a filesystem, you must:

Create an empty, non-sparse file that matches the size of the filesystem.

Get mapping from logical file positions to disk blocks.

Cancel this mapping so that you can map from disk blocks to logical file position. Of course, some blocks are inaccessible due to the use of the file system.

At this point, the disk looks like a raw disk that you are accessing with a disk block. It is a valid assumption that this block addressing is mostly monotonic for physical number cylinder. IOW, if you increase the disk block number, the cylinder number will never decrease (or never increase - depending on the LBA drive to the physical mapping order).

Also note that the average write rate can be set per cylinder or per storage unit. How do you know? You will need last issue and the only one the right way get it - compare it yourself. You need to fill the entire disk with data by repeatedly hitting the disk zero page, going through the block and dividing the total amount of data written by the amount it took. You need direct access to a disk or file. This should turn off OS buffering for file data and not filesystem metadata (unless using a raw disk).

At this point, all you have to do is write blocks of data of reasonable size at the two extreme values ​​of the block numbers: you need to fill the disk inward from both ends. The size of the data blocks depends on the loss of bandwidth you can allow for searches. You should also assume that the hard drive may need to be updated from time to time to update its service data. Assuming 15ms is required in the worst case, you are wasting 1.5% of your bandwidth per second for each search. Assuming you can save no more than 5% of bandwidth, with 1 lookup on average for the drive itself, you can look up twice per second. So your block size should be your_bandwith_per_second / 2. This bandwidth is not throughput disk, and the bandwidth of your data source.

Alas, if only where it is easy. Typically, it turns out that the bandwidth in the middle of the disk is not the average throughput. During the test, you should also pay attention to the write speed across the smaller partitions of the disk, say every 1% of the disk. This way, as you write to each section of the disk, you can figure out how to split the data between the "low" and "high" sections that you are writing. Suppose you start at 0% and 99% positions on the disk, and the bottom position has a bandwidth of mean * 1.5, and top position has a bandwidth of mean * 0.8, where mean is your desired mean bandwidth. Then you need to write 100% * 1.5 / (0.8 + 1.5) of the data to the low position and the rest (100% * 0.8 / (0.8 + 1.5)) to the slower high position.

Of course, this is the main difference between the two, but not the only one.

Types of computer memory

Computer memory is where data is stored. The memory is divided into ephemeral(For example, RAM or RAM), which only retains data as long as the computer is running, and permanent(non-volatile) that retains data even after power off.

It can also be divided by device, or rather by type. Can be distinguished magnetic media(e.g. hard drives HDD, SSHD), optical, semiconductor and flash memory.

Differences between HDDs and SSDs

Media design

The main difference that first comes to mind is the internal structure.

HDD hard drives are magnetic media information. To read them, a special, movable head is used, which moves along the circular magnetic plates used for storing data, and thus searches for files.

SSD media are classified as flash memory built from cells only NAND Flash... This allows you to read and write files on the SSD much faster - all due to the fact that reading occurs without the participation of moving elements. Moving parts must arrive at the location of the file and cannot be present in multiple locations at the same time (which further slows down reading or writing multiple files).

Loudness during operation and resistance to damage

Moving elements are also responsible for the noise generated during the disc operation. Deprived of these moving parts, SSDs run silently. In addition, they are also more resistant to damage (again this is due to the lack of mechanical parts that can move, for example, in the event of a fall).

The AHCI protocol was created for tough HDD disks, at a time when no one yet expected the emergence of faster carriers. Later SSDs had huge potential in terms of data flow, however, it was severely limited by the legacy protocol.

For new fast hard disks, a new NVMe protocol was created. Its capabilities are shown in the table below:

12.03.2010, 23:49

I would like to hear an opinion experienced users information on this topic.
It is interesting to know at what speed it is better to write discs, say, if the DVD + R costs 16X, then at what speed you can write without losing quality. It is clear that the lower the speed, the more reliable and better quality, but still many have experience and would like to hear it.
The point is to save time, if necessary, and the quality at the output is normal.

13.03.2010, 00:02

In my opinion, the eighth is the optimal one - both reliably and relatively quickly.

13.03.2010, 02:28

Write at half the declared speed and you will be happy. Except for the top brands, this applies to all DVD discs.

13.03.2010, 09:13

The question arose after installing new Pioneer drives. They somehow started to write everything at maximum speed and without any problems. Before that, there were NEC drives and Nero produced it on cheap discs like it is impossible to record at such a speed, but only at a lower one. So I thought that it is possible to do this, write at maximum speed, or it is better not to risk it.
Thank you all for your advice.

13.03.2010, 21:34

13.03.2010, 23:27

It is better not to write at maximum speeds. There is a risk of not signing up. In addition, if you then turn on such discs on old players or with a tired laser, it may be difficult to read.
So it turns out that at what speed is the disc recorded, only at this speed is it readable later? It’s just that the logic is so clear that it’s not enough to write down, you still have to read it later.

14.03.2010, 00:38

The write speed is not related to the subsequent read speed.
On the branch are given practical advice... But, it is advisable that you personally screw up a few discs, then the meaning of all that has been said will reach faster. You need to take into account everything in the complex:
-Technical specifications drive (including firmware updates, as they may become obsolete as new types of media become available)
- Computer parameters (a weak horse will not pull a powerful, ultra-modern drive at the top of its capabilities).
-Skill use and choice of blank (the pursuit of "cheapness" often turns into an imaginary disappointment in the drive, or in the software)
-Soft used for recording. (Outdated software does not understand the latest drives, or blanks)
All these skills and abilities will appear with experience, and of course there will be not a single screwed up disc (as an inevitable payment for acquiring this very experience).

14.03.2010, 05:59

There are three speeds - 4x, 6x, 8x, all the rest is a game! Then everything depends on the disc, drive, recording program and the number of simultaneously recorded discs. The blanks, the best real Made in TAIWAN, for example from RITEK, the main thing is that they are real from there. The new drives are all good, but the speed of dying is different. In general, the drives are very controversial issue... Personally, I will advise PIONEER how the best option, but PIONEER doesn't like "+" blanks very much. In general, the drives are not very fond of them. It is better to write from an image, especially if you write several discs at the same time. There are many programs, but if you are too lazy to try, choose Alcohol, you can't go wrong. If you write films images, create ClonDVD, and write Alcohol. If everything is fine, write on 6x - 8x, if you doubt something on 4x.

14.03.2010, 06:51

Nero, a program for housewives (just for recording), even if there is an extension for recording several discs at the same time, the other has good solutions. But in the other you do not risk, and in the recording you risk a disc. The pioneer makes good drives, but best pioneers in Russia you cannot buy, for example, DVR-S16FXB, etc. Choose blanks better "-", especially disposable ones. "+" write at lower speeds, but a lot depends on the disc itself. Speeds other than 4-6-8 are either a waste of time or a risk.

14.03.2010, 09:24

I listened to amateurs - it's funny! Listen to the pros. There are three speeds - 4x, 6x, 8x
Did you tell Verbatim that? And then these lamers are not aware of the latest trends and continue to make 16x blanks. Although - where are they to RITEK ...

If you write films images, create ClonDVD, but write Alcohol

14.03.2010, 10:03

Did you tell Verbatim that? And then these lamers are not aware of the latest trends and continue to make 16x blanks. Although - where are they to RITEK ...

This is provided that the original from which the image was taken is stamped / recorded in full compliance with the DVD-Video standard. In it (the standard), as all "pros" know, an important role is played, among other things, by the physical location of files on the disk. Place correctly DVD-Video files when recording can only ImgBurn program... And Alcohol will simply make an identical copy of the original with all its errors and inaccuracies.

100%, or, "the same end and the same place."

Various: Traksdata, Ridata, Arita are good when cheap blanks are needed.

The originals from the discs are removed by whatever they want, they arrange their menus, tracks, etc. and they lose files.
I have downloaded films several times already.
Therefore, sometimes I "skip" (just check), a movie through DVD_Shrink and then I record ONLY ImgBurn.
I don't use alcohol at all - I put A-52 a couple of times - I had to bypass the protection, NERO - 6, when they upload the image taken by NERO.
I write 4, rarely 8 - "God protects the gentleman."

15.03.2010, 23:10

16.03.2010, 01:50

If she signs up, then everything will be fine.
In 98 percent, this disc will still be written. If you do not run into frank trash.
But the percentage of reading these discs will decrease back in proportion to the increase in speed ... The more doubtful the device, the higher the chance to see the inscription "no disc" ...

The optimal speed is 4.
The maximum speed can be set only on very famous brands and with a very big rush. Everything else is either 4th speed or half of the maximum. And you will be happy ...

16.03.2010, 08:42

From all of the above, I conclude that you can write at any speed, you only risk screwing up the disc. If she signs up, then everything will be fine.

Take a simpler look at this. If you don't rush - better speed 4 or 6.
If you are doing a game and there is not enough time - 8.
And turn the less on what is written on the discs. Now almost everything is done in Odessa on Malaya Arnautskaya.

16.03.2010, 09:15

The question arose purely due to the fact that you don't need to constantly do anything, but from time to time you need to do a certain amount, and this is where this question of time arises. If I could find its retarder, then at least at the second speed it would be possible to write, but sometimes I will make the choice on the 8th or 16th question in time or not :(. There are cheap discs, when you insert them, the program itself gives out that you can write them only on 4. Whatever speed you set yourself, write only on 4x, there are 8x, even 12x, but there are some that can be written on 16x even more expensive.

Basically I write in 8x, but I had to do it several times already in 16x, so I'm worried, will they come back? :) While silence, ugh, ugh, ugh.

16.03.2010, 23:46

"... From all of the above, I conclude that you can write at any speed, you only run the risk of screwing up the disc. If it does, then everything will be fine ...."
======================================================
Well, in short, yes. Try to avoid "new, single speed" discs. On which the speed formula is indicated by one value, for example X16. Preferred blanks for a range, for example 1-16x.
Otherwise, the recording may fail, since the disc is optimized for high speed writing, and when trying to write at a reduced speed (for example, if the drive has a maximum speed of 8), it is quite possible to screw up the disc.
This is a small but very useful nuance.
In general, I personally never write at 16 speed, and as I see, I'm not the only one here. Even the eighth speed is already very, very decent.

17.03.2010, 01:04

Speed ​​- maximum 8
Progs - ImgBurm, or DVDecriptor (if paired with DVDshrink), the rest is from the crafty one, or if the above written for some reason went wrong.
This is my IMHO.

17.03.2010, 07:41

It all depends on the quality of the source. The speed is better than 6 or 8. It is better to take blanks well-known firms, on the left discs and the record will turn out like this. The higher the write speed, the faster the drive will wear out. How many drives I haven’t bought, they don’t last for more than a year.

What is CD Recordable?

Recordable CDs or CD-Rs are discs produced using a technology that allows the user to create his own CD in one of the industrial formats. This technology uses discs as a basis for write once(WORM - Write Once, Read Many) standardized by Philips and Sony and described in the corresponding documentation (Orange Book, Part II). In order to create a disc yourself, you need to have a blank CD-R disc, a recording device - CD recorder (CD Recorder) and the corresponding software.

What are CD-R discs used for?

All industry standard CDs can be created on these media, including audio discs (CD-DA), video discs (Video CD), data discs (CD-ROM), photographs (Photo CD). CD-R discs allow you to store a very large amount of information: up to 650 MB of data or 74 minutes of high-quality stereo sound. Moreover, for Lately widespread CD-R discs of larger capacity: 700 MB of data or 80 min. sound and even larger discs.

Yes, CD-R discs are fully compatible, i.e. if it is correctly recorded and correct equipment and a high-quality CD-R matrix were used for recording, then this disc will be read without problems by all devices: CD-ROM drives, Audio and Video CD players, as well as new DVD players. However, it should be remembered that the first drives were designed and produced at a time when CD-R disks were not yet available. Therefore, if you are using a very old device (pre-1994), there may still be reading problems.

What is the writing speed of a CD-R disc?

The term "write speed" defines how quickly data can be written to a CD-R disc. Marking 2x, 4x, 6x, 8x, 12x, 16x, 24x, ... 48x shows how many times faster the device writes data compared to the single-speed reference. One speed is understood as a data transfer rate equal to 150 Kb / s. Thus, marking 2x means that data can be written at a speed of 300 Kb / s, 8x - 1.2 MB / s, 16x - 2.4 MB / s, 48x - 7.2 MB / s. Please note that the actual speed may vary depending on the selected recording format, since data is recorded in the 2 "048 bytes per block mode, and the audio information in the 2" mode 352 bytes per block. Therefore, the actual recording time of one full disc may differ slightly depending on the format.

Typically, CD-ROM drives are labeled with a single digit indicating the maximum speed at which data can be read. In this case, the fastest format for reading is indicated - CD-ROM Mode 1, moreover, moreover, when measured on the outer perimeter of the disk. The marking of CD recorders contains three numbers: the first is the writing speed of CD-R discs, the second is the rewriting speed (CD-RW discs), and the third is the reading speed. Accordingly, marking 16x10x40 for a CD recorder means that it is capable of recording CD-R discs at 2.4 MB / s, CD-RW discs at 1.5 MB / s, and reading discs at 6 MB / s. If the marking consists of two numbers (usually, only for old recorders), then this means that such a drive cannot work with CD-RW discs.

What is disc-at-once (DAO) disc burning - disc at once?

This is a recording mode when a disc is recorded immediately from beginning to end, without interruptions. Those. the laser beam turns on at the beginning of the disc recording, and turns off only at the end of the recording.

First, special information is written to the disk, marking the beginning of the recording (lead-in), then the data itself, and at the end the final information (lead-out). As a rule, the DAO method is preferable if the disc is later transferred to the factory for replication, and the recordable CD-R is the master disc. Recording in DAO mode allows you to avoid bundles of input (run-in) and output (run-out) blocks, which are associated with multisession recording by mastering equipment and make the disc unsuitable for making a matrix from which the circulation will be produced.

What is track-at-once (TAO) disc recording - track at once?

The TAO recording mode allows you to record a disc not immediately from beginning to end, but in several passes: initially you can record one audio track (track) on a disc, then another, and so on. Accordingly, as many tracks are recorded on the disc, the laser beam will turn on and off as many times during recording. Switching on / off the laser is perceived by sound players as a pause between tracks lasting 2 seconds. It should be noted that an audio disc recorded in this way can only be read on a regular CD player after the table of content (TOC) has been written. After TOC has been recorded, it is not possible to add tracks to the disc.

What is session-at-once (SAO) disc burning - session outright?

The SAO recording mode is usually used when recording the CD-Extra format, a format that combines audio part (CD-DA format) and software part (CD-ROM format) on a disc. When recording in SAO mode, the laser beam turns on at the beginning of recording the audio part, turns off at the end of recording tracks, then turns on at the beginning of recording a part of data and turns off at the end of the recording. The TAO mode is also applicable for preparing CD-Extra format discs. In this case, during the recording of the sound part, the laser will be turned on / off as many times as it is scratchy on the track disc.

What is multisession recording mode?

A multisession is a recording mode that allows you to re-record a CD, that is, add new information to the previously recorded one. Each session contains a record of the beginning of the session (lead-in), then the data itself and the final information about the session (lead-out). Unlike disc-at-once recording or injection-molded CD, there can be up to 99 such sessions on one disc.

When recording in multisession mode, information about the structure of previous recordings is copied to the new session and can be corrected. Thus, when recording in multisession mode, the user can destroy information about the structure of already unnecessary or obsolete records without including it in a new table of content (TOC - table of content). This means that it becomes possible to "erase" unnecessary information from the CD, although in fact, it physically continues to remain on the disk and can be restored using special software.

The disadvantage of the multisession mode is that the disk space is wasted, since separating one session from another, about 13.5 MB (6 "750 blocks) are lost each time. The more sessions recorded on the disk, the more space is lost for the session separators. , some older CD-ROMs (usually before 1994) cannot read multisession discs.

What is the difference between discs recorded in multisession and multitrack mode?

A session is a complete record on a data CD that has a lead-in and a lead-out mark. A disc can contain from 1 to 99 sessions. The same, but when applied to audio discs, it is called a track (track). Each of the tracks has index numbers in the subchannel, which are differentiated from one another and allow selective recording.

When recording software disks in multisession mode, the disk is readable after at least one session has been written, since the table of content (TOC) is written at the end of the session and is updated every time a new one is written. On audio discs, the TOC is recorded at the beginning, so it cannot be updated. Thus, the audio disc can only be read after the TOC has been written. However, such a disc can be read without a TOC, but only on a CD recorder.

When recording an audio disc in multitrack mode, the recording software reserves space at the beginning of the disc under the TOC. After the disc is finally formed, the TOC is recorded.

What kind CD-R varieties disks are there?

Depending on the application, all CD-R discs are categorized into brand-name (BN) versions and production (or OEM) versions. Discs BN versions are characterized by the fact that they are produced with the manufacturer's logo already applied to the surface of the disc. Such discs are usually sold at retail and are an acceptable solution for those who are going to store data archives on them, from time to time create music collections, etc. The inscriptions on such discs can be applied with a special marker or felt-tip pen. Usually BN discs are sold packed in plastic boxes (jewel cases) or envelopes.

Discs for production or OEM, do not have any logo on their outer surface, their surface is "clean". And although on it, just like on the surface of BN discs, you can make inscriptions with a marker, OEM discs are nevertheless intended for printing text and graphics on their surface using special CD printers (for more details, see the CD / DVD printers page) or applying your own logo using silkscreen or offset printing. OEM discs are packed in such a way that it is possible to include them in the production technological chain as conveniently as possible. The most common types of packaging are bulk and spindle.

It should be noted that disks for production or OEM are more multifunctional (in the sense of applying a design on them) and cheaper than BN disks, which makes sense to purchase when the total monthly demand for disks does not exceed several dozen pieces and there are no special requirements for them. registration.

BN discs have another feature: they can be sold under their own logos of companies that have nothing to do with the production. Actually, everyone can release their own brand. This creates a lot of confusion. So, for example, under Philips brand you can find discs produced by Taiyo Yuden, Ritek, CMC. Until 1998, the Traxdata brand hid exclusively Kodak, and now the same Ritek and CMC. There are dozens of CD-R disc manufacturers in the world, and there are thousands of brands.

What is a CD-R disc?

These are discs designed to be burned in CD duplicators. The bottom line is that duplicators are devices specifically designed for mass production replicating CD-R or CD-RW discs in which a large number of high speed recorders. Accordingly, in the main data transfer bus (usually a high-speed SCSI bus), the process of multiplexing ("distributing") a signal across devices in real time is actively proceeding. Therefore, the requirements for the synchronization of processes are especially high. CD-R discs, synchronously matched by parameters, are preferable for recording on duplicators.

Discs from leading manufacturers such as Taiyo Yuden, Mitsui Toatsu, TDK, Kodak, Ricoh, Verbatim, Ritek, Princo and others do not need to be matched and are suitable both for recording in stand-alone recorders and duplicators. In this case, the marking indicates discs without a logo, intended for labeling on a CD printer.

Why do some manufacturers indicate the size of 650 MB, and others 680 MB, although the size in minutes is always the same and is 74?

74 minutes can be converted to data bytes by multiplying 75 blocks per second (baud rate when reading audio) by 60 seconds (1 minute). Each block contains 2 "048 bytes. Thus, a 74-minute disc of 333" 000 blocks contains 681 "984" 000 bytes. 650 MB is obtained by dividing the number of bytes by 1 "024 to convert bytes to kilobytes and by 1" 024 to convert kilobytes to megabytes. 680 MB is obtained if we assume that 1 KB is equal to 1 "000 bytes, and not 1" 024, as it really is.

Thus, it becomes clear that the discrepancy in the prefix "kilo" (in general case it is equal to 1 "000, but in computing technology 1 "024), which gives rise to the difference in marking.

What does the inscription "Certified for recording at speeds 1-16" mean on CD-R discs?

This means that the CD-R manufacturer guarantees the normal quality of the disc when recording at speeds from 1x to 16x. When selecting the write speed, use only the maximum permissible value by the manufacturer of the disc. Do not be deceived by the situation when, having bought a cheaper 8x disc, you burned it normally at 16x - violation of the recording mode may manifest itself in an unexpected loss of information or other "surprises". Remember that the task is not only to successfully write data to disk, but also to read them reliably from there.

On the packaging, the speed of the disc is usually indicated maximum value recordings: 12x CD-R, 16x CD-R. Sometimes the designation is written in the 1-16x CD-R style and even with an explicit listing of all write speeds.

If you burn a 1-16x CD-R disc at 2x and 16x speeds, which copy will be better?

In general, there is no dependence of the write speed on the read speed. Therefore, if the disc is intended for recording in the speed range from 1x to 16x, then you can choose any convenient speed. However, if you go deeply into this issue, then the higher the write speed of the disc, the potentially higher its quality. Rather, with an increase in the write speed, there is a chance to improve several indicators of the disc, including one of the main ones - BLER.

The abbreviation BLER is disclosed as and denotes the frequency of occurrence of blocks of information that have erroneous characters (bytes) detected at the first level of error detection and correction C1. BLER is a parameter that well reflects the quality of a disc as a whole, as it depends on many factors that appear during the manufacturing process of discs.

The Red Book standard defines the maximum BLER<= 220 блоков в секунду. При этом вычисляется среднее значение при измерении на интервалах по 10 секунд. В зависимости от BLER диски делятся на несколько классов (grade) качества:

• Grade A (BLER< 6) - диски высокого качества;
• Grade B (BLER< 50) - диски хорошего качества;
• Grade C (BLER< 100) - диски удовлетворительного качества.
• Grade D (BLER< 220) - диски, которые можно использовать, но чтение информации с которых затруднено или велика опасность выхода диска из строя (потеря информации).

Potentially, CD-DA discs can have a higher BLER than CD-ROM discs (it is no coincidence that the Red Book allows a fairly high BLER - up to 220). However, the lifespan of an audio disc is usually incomparably longer than that of a disc with programs - music programs are much less susceptible (or not at all) to obsolescence in comparison with modern software. A high BLER indicates not only the danger of data loss, which is incompatible with the long life of the disk, but also about possible reading problems in some drives. Therefore, in practice, the leading CD manufacturers try to manufacture their products with BLER< 50 (Grade B). CD-R технология позволяет легко наладить производство тиражей с BLER < 20 без дополнительных затрат. А если применять только диски известных производителей, то 100% выход дисков высшего класса качества (Grade A) практически обеспечен.

If we take a disc certified for 1-16x write speed, write the same copy of it at each speed, and then "run" the discs through a quality analyzer (for example, Clover QA-201D) and measure the BLER, we will find that it decreases slightly at increasing the speed, which means that the discs benefit in quality. But the increase is so insignificant that the quality improvement with the speed increase can only be considered a theoretical parameter. However, one can unequivocally refute the erroneous judgments that "the lower the speed, the higher the recording quality."

You are talking about BLER and all sorts of obscure things. And I burned a disc at 2x and it is readable everywhere, and a disc recorded at 16x cannot be read anywhere, even on a "native" recorder.

The aforementioned about some improvement in quality when recording at a higher speed is true only in the case when working equipment is used and the CD-R disc is really intended for recording at high speed.

Manufacturers of high-speed (12x or more) recorders give recommendations on the type of computer and the type of CD-R to be used in order for the disc to be written successfully. If you follow these guidelines, all discs recorded at different speeds will be nearly identical, regardless of write speed. But vendors often claim that their drives are 16x certified, when in fact they are not. In addition, if you have a working recorder (in this regard, the drive is simply "loose") or a recorder installed in a computer case, the cooling of which does not ensure its normal operation, the recording results may not be predictable. That is why, with a serious approach in studio conditions, the quality of the recorded disc is necessarily checked using a CD / CD-R disc analyzer (for example, Clover QA-201D).

Will discs burned at 4x or 8x speeds be read on 20x or 40x speed CD-ROM drives?

Yes, they will. The write speed is independent of the read speed and vice versa.

What's the difference between 74 and 80 minute discs? What drives are the information stored more reliably?

Originally, the Red Book audio CD standard called for CDs that could store 74 minutes of stereo sound. This corresponded to a data volume of 650 MB. Therefore, after CDs began to be used for storing computer data, the question of the maximum capacity did not arise - the same value of 650 MB was adopted. Then the same capacity migrated to the standard CD-R discs.

However, over time, the gigantic value of 650 MB has ceased to be not only gigantic, but simply large. A desire has arisen to increase the capacity of disks for the needs of storing digital video and data. But by the time the question became this way, there were already hundreds of millions of different CD-ROM drives (CD-ROMs, audio and video players) around the world that the newer, larger discs needed to be compatible with.

The developers took a relatively simple path: they simply "rolled up the spiral" (the path along which the laser beam moves from the center to the edge of the disc) of the injection dies from which CD-Rs are cast, thus obtaining additional capacity. At the same time, compatibility problems did not arise, since the accuracy inherent in the reading drives made it possible to track a "tighter" spiral. At the same time, however, all the leading manufacturers of CD-R discs honestly warned users about some non-standard novelty.

But the chase for extra capacity didn't end there. There are discs with a capacity of 90 and even 99 minutes! In the latter case, the spiral was "rolled up" so "tight" that CD-Rs made in this way were recorded and read only by selected drive models.

So the default is 650MB of disk space. Practice has shown the reliability of using 700 MB disks. Storing data on larger disks, on the other hand, risks exposing yourself to read / write incompatibilities.

How long can CD-R discs be stored unburned?

CD-R disc manufacturers estimate that unrecorded discs have a shelf life of 5 to 10 years, depending on the disc model.

How long can the recorded data be stored on a CD-R?

Since CD-R discs have recently become widespread, a recognized way to extrapolate their lifespan is to perform accelerated aging tests, which are traditionally used in laboratories to determine the performance of CD-R discs in the future. Improper testing or measurement procedure can seriously affect the estimation of the information retention period. The ANSI committee has developed recommendations on which it will be possible to determine the shelf life of information on CD-R.

The main factors affecting the longevity of the medium are: the stability of the state of the active layer and the storage conditions of CD-R discs. The media's ability to retain data recorded on it is measured according to the BLER industry specifications. For high-quality disks, after a test for the impact of the external environment in conditions of increased aggressiveness, the average BLER value should increase only enough so as not to jeopardize the stored data and remain within the limits determined by the class.

Recordable CD manufacturers have conducted repeated studies using industrial tests and mathematical modeling techniques, and have found that CD-R discs have a shelf life of 70 (regular models) to 200 (improved models) years. The storage time of information on ordinary CDs is indicated at 25 years, but you can already observe the failure of disks that were made in violation of technology and without special tests - the oldest CDs that were released in 1980 are more than 20 years old - an age sufficient to make direct conclusions.

What is finalization and fixation of a CD-R disc?

Finalization is the process that completes the recording of a session, i.e. if a session is written to the disk, then it must end with a finalization record representing the table of content (TOC) of the session. If subsequent sessions are recorded on the same disc, then each of them must end with a finalization recording. Finalization is required in order for the CD-ROM drive to read the CD.

If the CD is finalized in its entirety, or it would be more correct to say fixed, then it is impossible to add sessions to it, even if there is still free space on the disk.

What is incremental writing and packet writing?

TAO (track-at-once) is a form of incremental recording that uses a minimum track length of 300 blocks and a maximum number of up to 99 tracks on a disc. A disc recorded in TAO mode has 150 blocks reserved for recording track start information (run-in), recording of the end of a track (run-out), recording of the gap between tracks (pregap), recording of a linking of tracks (linking). In general, to create each session, you need to write more than 12 MB of overhead to disk. Recording in packet (packet) mode allows you to make several records within one track and thus avoid the loss of blocks for the finalization of the session. In this mode, only 7 blocks are reserved for the beginning, end and bundle.

All CD recorders on the market are currently supplied with the packet writing driver. Externally, work in the packet writing mode looks like it is writing to a conventional logical device: you can write data from any application to a CD-R disk, erase them, rename files and directories. The exception is that after erasing the information, the volume of the disk does not increase: the deleted information is only hidden, but not physically deleted.

Disks that were written to in batch mode do not contain finalization recording, therefore they can be read only on the device with which the packet recording driver is installed. Nevertheless, packet writing is extremely convenient for archival storage of information, and to achieve read compatibility, the following is done: during preliminary formatting of a disk (when using packet writing, disks must be formatted beforehand), a "normal" session containing the packet writing driver is first placed on the disk , and then the space for the packet recording itself is already marked. If such a disk is placed in a drive that was not originally intended to read disks written in this way, then it is always possible to first read and install the driver from the "normal" part of the disk, and then start reading data written in batch mode.

The use of packet writing with CD-RW discs is completely similar to recording CD-R discs in this mode, with the only difference that data from a CD-RW disc can be deleted physically, and the disc itself can be used again.