Solid state drives (SSD) - advantages and disadvantages
First, let's understand the definitions. Hard and solid - what's the difference?
What is a hard drive, which is also very often called HDD, hard drive, hard, screw, etc.?
HDD (English hard disk drive) is a data storage device based on the principle of magnetic recording. Information is recorded on plates covered with a layer of ferromagnet. The discs are mounted on a spindle that rotates at a very high speed (up to 15,000 rpm). In addition to the mechanical part, there is also an electronics unit, in fact, which controls the entire mechanics of the device.
The first serial hard drive was produced by IBM in 1956, weighed 971 kg, had a total memory capacity of about 3.5 megabytes. History developed rapidly, and by 2011 1 terabyte became the norm for a hard drive. At the moment, there are two and even three terabyte drives.
The principle of operation of a hard disk is based on recording changes in the magnetic field near the disk head.
The main players in the hard drive market are Fujitsu, Seagate, Western Digital, Samsung, Hitachi.
The more the volume of hard drives became, the more the volume of transmitted information became. In the general mechanical structure of the hard drive lies its main drawback - a relatively low amount of transmitted data per second (average models of manufacturers at the moment have an established data transfer rate of about 100-150 Mb / s). In addition, the higher the data transfer rate, the more hot the hard drive gets.
For many tasks, as well as for everyday use of a computer, these speeds are quite enough, however, with specialized use (graphics stations, professional gaming computers, computing centers, etc.), it is the hard disk that imposes significant restrictions on the overall performance of the system.
The first developments on the invention of a fundamentally new carrier began in the 1970s. In 1978, StorageTek introduced the first state-of-the-art solid state drive, laying the foundation for the development of solid state drives. And only in 2008, the South Korean company managed to create the first 128 GB SSD, similar to modern counterparts, which it demonstrated at an exhibition in Seoul.
Mass production was only organized in 2009. At the moment, there are 720 GB drives, the cost of which starts from 60,000 rubles, for example, the IBIS OCZ 3HSD1IBS1-720G model from the OCZ company.
So what is an SSD
Translated from English, solid-state drive means "a disk without moving parts." A solid-state drive is a storage device whose principle of operation is based on the use of rewritable microcircuits and a controller. Often users confuse terminology and call an SSD a hard drive. This is wrong due to the technical nature of solid-state drives. A distinctive feature of this type of media from an HDD is that when reading data from an SSD, there is no need to perform mechanical operations, all the time is spent only on transferring the address and the block itself. Accordingly, the faster the device and controller memory itself, the faster the data is shared.
However, the process of changing or erasing data from SSDs is not so simple. This is due to the fact that memory is written in 4 KB blocks and erased in 512 KB blocks.
When modifying blocks, the following sequence of actions occurs:
1. The block containing the changes is read into the internal buffer.
2. The necessary modification of the bytes is made.
3. The block is erased from flash memory.
4. The new location of the given block is calculated.
5. The block is written to a new location.
During the deletion of files, they are not physically deleted, but only marked by the system as deleted, however, the SSD does not know which data is user and which is deleted, and in fact, all blocks have to be processed according to the above scheme. This system leads to the fact that with a large amount of data on the disk, the total operating time increases significantly, which slows down all work.
SSD security and reliability
If we talk about the possibility of data recovery from SSD, then the following points can be noted:
- The data is not deleted immediately, like in the HDD, even if you overwrite the file at the top with other data.
- The data recovery process is quite time consuming, due to the fact that it is necessary to choose the correct order, combine the results, and also select the necessary algorithm that emulates the operation of the media controller.
The reliability of an SSD directly depends on the reliability of the controller and its firmware, since it is the controller that is located between the interface and the memory chips and the likelihood of its damage in case of power failure is very high.
Rules for working with solid media to extend their life cycle and increase overall speed:
- All data that changes frequently (various temporary data, swop files, etc.), transfer to a regular HDD.
- Disable disk defragmentation.
- Update the controller firmware periodically.
- Leaving about 20% of the disk partition permanently free will improve overall performance.
Advantages of SSDs over hard drives:
- Very high read speed of data blocks, which is actually limited only by the bandwidth of the controller interface.
- Low power consumption.
- Silence.
- No mechanical parts, resulting in fewer possible breakdowns.
- Small overall dimensions.
- High temperature resistance.
Disadvantages of SSD:
- A limited number of cycles of rewriting memory cells (from 10,000 to 100,000 times). When the limit is reached, your drive will simply stop working.
- High price. Compared to the price of a 1 GB HDD (about RUB 1.6 / GB for a 1 TB HDD versus RUB 48 / GB for a 128 GB SSD).
- Low disk space compared to HDD.
- The problem of compatibility with some versions of operating systems (some operating systems simply do not take into account the specifics of solid-state media, which leads to very rapid wear of the media).
SSD companies and manufacturers you can safely trust:
Examples of models:
The average cost is 15,000 rubles.
An excellent member of the solid-state family, with a read speed of up to 355 MB / s and a write speed of up to 215 MB / s, it connects via a SATA 6 Gb / s interface.
128Gb Kingston SV100S2 / 128G SATA 2.5 "V100-Series
Average price - 6000 rubles.
A good SSD with a SATA-2 connection interface. According to the manufacturer's specifications - write speed up to 230 MB / s, read speed up to 250 MB / s.
SSD Corsair CSSD-V64GB2-BRKT
Cheaper drive, smaller in size, with a SATA connection interface.
Average cost - 3700 rubles. It has a write speed of up to 130 MB / s and a read speed of up to 215 MB / s.
conclusions
At this stage of technological development, when solid-state media are almost 30 times more expensive than hard drives at the price of 1 gigabyte, the advisability of using an SSD in the everyday life of an ordinary user is controversial, but if you want to speed up the boot time of the operating system and brag about it to your friends, then SSD is definitely For you. It is justified to use SSD in mobile devices, servers with a high load on the disk system, as well as in cases where professional applications that require high speed data access are used.
The abbreviation HDD - hard-disk drive - many have already remembered and understand that this is a hard drive. But what is SSD - a new acronym that has been used more often than HDD in recent years? Read about it in our article.
SSD: decryption
SSD stands for solid-state drive and is translated into Russian as "solid state drive" or, less accurately, "solid state drive". This acronym hides a new storage technology that is more advanced than traditional hard drives.
SSD storage: what is it?
So what is an SSD drive? The main feature of such a drive is the absence of moving parts. In conventional hard drives, data is stored on rotating platters, and this rotation causes a number of disadvantages: firstly, it slows down the reading of data, secondly, it accelerates wear and tear of the drive and makes it more vulnerable to shock, and thirdly, it generates noise at work.
Nothing rotates in an SSD - data is stored here in flash memory, but written and erased using electrical charges. This makes SSDs very fast, they don't make any sounds, and they can withstand bumps and falls more easily.
True, this technology has its drawbacks. SSDs cost significantly more than hard drives of comparable capacity. In addition, the specifics of flash technology imposes a limit on the number of rewriting cycles, so in theory SSDs can fail earlier than hard drives, although in practice modern solid-state drives are quite able to successfully withstand the average lifespan of a typical user computer.
What is an SSD for
Since a solid-state drive, as mentioned above, is not the cheapest pleasure, it is not worth thoughtlessly buying it to replace a regular hard drive. For storing large amounts of data that does not require high read speeds, SSDs are still not the best choice. You should not use it for those files that are repeatedly overwritten during the day, otherwise the life of the drive will quickly come to an end.
It is best to install an operating system on the SSD - then it will work much faster. Both applications and games will benefit from this, for which a high speed of reading data from a drive is important. Read about how to install a solid state drive in our article. And for storing files, you should equip your computer with a second disk - a traditional HDD.
Recently, solid-state drives have been increasingly installed on computers and laptops. So what is an SSD drive? In simple terms, this is a huge flash drive, only with faster read and write parameters. There is not a single mechanical part in an SSD. It consists of microcircuits only. Hard drives have a large amount of memory, but low speed, and solid-state drives, with a low capacity, have speeds several times faster than HDDs.
Features of work
Let's take a look at how HDD and SSD work when copying or reading small files. The smaller the file size, the greater the difference in speed between the hard drive and the solid state drive.
Imagine that your hard drive is a notebook with some information. And to find and add this information, you need to leaf through the notebook. And an SSD is a sheet of paper with data in full view. Accordingly, he will find information much faster.
HDD spends a lot of time on moving the read heads, on finding the necessary sectors on the magnetic platters. The SSD simply gives you the information you need. This happens when the system starts up, when copying or reading several thousand small files (for example, photos). Therefore, the speed of this type of media is several tens of times higher than that of HDD. Programs and the system itself installed on a solid state drive will start much faster than on a regular hard drive.
It is best to buy SSDs from manufacturers that have proven themselves on the positive side in the production of these products. These firms include Crucial, Kingston, Corsair, Samsung, Tohiba, Transcend, Intel, OCZ, SunDisk. You shouldn't buy solid state drives from Chinese brands or little-known companies. These are: Apacer, Silicon Power, A-Data.
Since most SSDs have a small amount of memory, but very high performance, they serve mainly to install an operating system and programs on them, to increase their boot speed.
disadvantages
The main disadvantages of solid state drives include their cost. Even SSDs with a small volume are much more expensive than conventional hard drives, and their prices fluctuate in different directions every year.
An SSD is a flash memory made up of thousands of cells that tend to wear out. Basically, wear occurs when writing information to disk. Cells fail much more slowly when reading. It is conventionally believed that the smaller the capacity of a solid-state drive, the more reliable it is, since it does not have additional microcircuits and consumes less power. But this is all in theory, and has not been confirmed in any way.
Another disadvantage of SSDs is the inability to recover data when deleted. If you accidentally have a power surge, then only a small board will burn in the hard disk, and the information that remains on the magnetic plates can be restored. The solid state drive fails completely with all the files on it.
pros
Read and write speed is one of the most important parameters of an SSD. For solid-state drives, this speed ranges from 150 to 560 mbps. A medium-priced disc can have read and write speeds in the range of 450 MB / s. Random access time is not counted for solid-state drives, since it is equal to 0.1 - 0.2 ms. SSDs have a SATA - 3 connector, so the same connector should be installed on the motherboard. Otherwise, the disc will not work at full capacity. Also, a solid state drive is much more durable than a regular hard drive. He is not afraid of blows or
falls.
So what should you choose?
Now you have an idea of what SSD drives are. Let's see when it makes sense to apply them.
Only one 320 GB hard disk can be installed for an office computer. If you play games, or you have a professional computer, then the best option is to install two discs. SSD sizes 60 - 128 GB. for installing programs, and the operating system, and a 1 - 2 TB hard drive. If you are using a laptop as an addition to your main computer, then it will be enough to install a hard drive with a capacity of up to 500 GB on it. If a laptop is the main computer, then it would be best to use a 750 GB HDD in it - or higher, depending on what purpose it is used for.
SSD (solid state drive, solid state drive, solid state drive- Russian) - information storage device based on chips non-volatile memory that retain data after power off. They are a relatively new type of storage media, and the first manifestation and development, non-volatile memory chips received from Flash drives and conventional RAM memory.
Contains the same I / O interfaces as modern ones. V SSD moving parts and elements are not used as in electromechanical devices (hard disks, floppy disks), which eliminates the possibility of mechanical wear.
Most modern solid state drives are based on non-volatile NAND memory. There are enterprise-class drives that use RAM memory, coupled with backup power systems. This gives very high data transfer rates, but the price of one gigabyte is very high by market standards.
Exists hybrid versions of SSD and HDD drives.
They include magnetic plates for a large amount of stored information and a small one in volume. SSD drive in one case. The most frequently used data is stored in SSD storage and are updated as they become relevant from the block HDD... When accessing this data, it is read at high speed from the solid-state memory without accessing the slower magnetic platters.
What are SSD drives made of .
* For example NAND memory
A solid state drive consists of the chips themselves NAND, which controls and brings all the functions, a volatile chip and a printed circuit board on which all this is soldered.
Sometimes in SSD drives used small battery so that when the power is turned off, all data from the cache could be overwritten in non-volatile memory and keep all data intact. There are precedents that in drives with MLC memory when the power was turned off, some or all of the data was lost. WITH SLC memory, no such problems were noticed.
Memory.
Nearly all high, mid, and budget solid state drives use non-volatile NAND(flash) memory due to its relatively low cost, the ability to save data without constantly maintaining power; and the ability to implement technology to save data in the event of an unexpected power outage.
Due to the compact layout of the chips, manufacturers can produce SSD drives in form factor 1.8; 2.5 ; 3.5 and less when it comes to devices without protective packaging. For example, for laptops or internal placement in a computer.
Most SSD drives are used cheap - memory that can fit in one cell more than one bit... This has a very effective effect on the price finished product and contributes to the popularization of these storage devices. But have MLC memory and big flaws. it low durability cells and more low speed write and read than drives based on.
SLC record only one bit into the cell and this provides up to 10 times better durability and up to 2 times more high speed versus MLC... There is also one drawback - price drives on SLC memory in about twice as high than the price of drives for MLC memory. This is due to high production costs, and especially because SLC chips the same volume is required on average twice as much to achieve the same volume compared to MLC.
SSD controller.
Almost all indicators SSD drive depend on the control controller. It includes microprocessor which manages all memory processes with a special firmware; and the bridge between the signals of memory chips and the computer bus ( SATA,).
Features of a modern SSD controller:
- TRIM.
- Reading, writing and caching.
- Error correction ( ECC).
- Encryption (AES).
- Possibility S.M.A.R.T monitoring.
- Marking and recording non-working blocks to add them to the black list.
- Data compression ( Sandforce controllers for example).
All memory controllers target parallel connected NAND memory. Since the memory bus of one chip is very small (maximum 16 bit), the buses of many chips connected in parallel are used (analogy RAID 0). Moreover, a single chip does not at all have excellent characteristics, but on the contrary. For example high delay input-output. When memory chips are connected in parallel, these delays are hidden, distributed among them. And the bus grows proportionally to each added chip, up to the maximum bandwidth of the controller.
Many controllers know how to use 6 Gbps, which is coupled with controllers supporting the data exchange rate 500mb / s, gives a tangible increase in read / write performance and full unlocking the potential of SSD drive.
Cache memory.
V SSD drives, cache memory is used in the form of volatile DRAM microcircuits, like in hard drives.
But in solid-state drives, it carries another important function... Part of the firmware and the most frequently changing data are in it, reducing the wear and tear of volatile NAND memory. In some controllers, the use of cache memory is not provided, but nevertheless they reach high rates in speed ().
Interfaces for connecting SSD.
The most common interfaces for SSD consumer grade are SATA 6Gb / s, and USB 3.0... All of these interfaces are capable of providing the required bandwidth for any SSD drive.
In portable devices such as laptops and tablets, the most common compact SSD drives with interface mini PCI-Express (mSATA ).
Advantages and disadvantages of SSDs versus HDDs.
Pros of SSD versus HDD(hard drives):
- They turn on instantly, do not require promotion.
- Significantly faster random access speed.
- Significantly faster access speed.
- The data transfer rate is much higher.
- No defragmentation required.
- Soundless, as they have no mechanical parts.
- They do not create vibrations.
- More resilient in terms of temperature, shock and vibration.
- Slightly less power consumption.
Cons of SSD versus HDD(hard drives).
- Cell wear. At least in SSD drives and there are no mechanical parts, memory chips wear out (mlc ~10000 rewrites, slc ~100000 ).
- The capacity is much smaller.
- The price is significantly higher in terms of GB / $
- Inability to recover lost data after command or just after formatting.
In solid state drives, the command (instruction) is used TRIM to increase the recording speed. Together with some microcontrollers, TRIM allows you to achieve a slight increase in reading speed. All SSDs released since 2012 are supported TRIM... In earlier versions, to enable this manual, you may need to flash new firmware. In most cases, flashing will permanently delete all data.
SSD storage devices are still a completely new generation of storage media and they are not balanced products in all respects. However, for enthusiasts, enterprise customers, and server-based deployments, they compare favorably in terms of performance, which can be a deciding buying factor. New round of evolution, solid-state drives will receive with mass production of memory chips Ferroelectric RAM (FRAM, FeRAM). This will increase the level of durability of the cells. SSD drives.
But not the fact that for SSD drives the future. Each new technical process, as practice has shown, reduces the read / write speed and increases the number of errors that occur, which also need to be removed using an error correction system to the detriment of performance. And for SLC this figure is acceptable, but with MLC and TLC (triple level cell) everything is very, very sad. With each new generation, without significant new breakthroughs, the speed will drop. And by 4 nm, it will drop almost to the level HDD 2012.
The emergence of a relatively new storage technology on the market raises many questions from users. What is SSD? Should I put it instead of the usual hard drive? Is he as good as they say he is? After reading this article to the end, you will answer all the questions posed, which will allow you to decide whether you need to change something in the way your computer works.
Let's start with the concept: An SSD is a solid state drive that uses NAND memory, which does not require electricity to store data. In fact, an SSD is a capacious flash drive that has a high speed of writing and reading information.
Comparison with HDD
To draw parallels with a conventional hard drive, you first need to go a little deeper into theory and see how the HDD works.
An HDD is a collection of metal disks that rotate on a spindle. Information is written onto the surface of the discs by a small mechanical head. When you copy something, create a new file or run a program, the head moves, looking for a place to write. For clarity, imagine a vinyl record - only instead of a needle there will be a mechanical read head.
Solid state drives do not have any moving mechanical parts.
Other advantages of SSD:
- Quick response to user actions.
- Silent work.
- Low power consumption (half that of HDD).
- No overheating.
These are just the main advantages of solid state drives that the user can "feel". However, the question of which is better than HDD or SSD continues to be asked by many users, so let's compare the characteristics of these two types of drives:
- The speed of the SSD is higher, since the stage of the mechanical search for the right place on the disk surface disappears. The data access time is reduced by 100 times - the system installed on the SSD literally starts to fly compared to using the HDD.
- The absence of mechanical moving parts contributes to the silent operation of the drive and an increase in its lifespan. HDD most often fails due to mechanical damage - SSD does not have such a problem.
- The SSD temperature is always kept at an optimal level, even if it is not cooled with a cooler. The HDD, on the other hand, overheats without cooling, which leads to software and hardware problems.
But let's be objective: SSDs also have disadvantages. First of all, this is the price, which is still quite high and directly depends on the volume. Another problem is the limitation on the number of rewrite cycles. HDD can be filled with data and cleaned up as much as necessary; SSDs have a limitation, but in practice it is difficult to achieve.
All SSDs are warranted for 3-5 years, but they usually last much longer, so don't focus on those numbers.
If you cannot choose between SSD and HDD, then there is a hybrid option - SSHD. Such drives combine the advantages of both technologies, but you will notice an increase in operating speed only when the operating system boots. Data recording and reading will be performed at the same level as that of HDD, therefore such hybrids are not very popular among users.
Selection rules
So, you have decided that it is time to abandon the outdated hard drive and install a solid-state drive in your computer - you figured out why you need it and what advantages it has over HDD. However, this raises another question: how to choose an SSD?
The stores offer drives in different form factors, controllers and prices, so it's hard to figure out right off the bat which one is right for you. In order not to feel insecure in a conversation with a consultant who will probably want to sell an SSD at a higher price, try to choose a drive according to the parameters below.
Volume
As already noted, one of the main disadvantages of SSDs is the price, which is rigidly tied to the volume of the drive. The minimum capacity today is 60 GB. If we consider that the installed Windows 7 requires 16-20 GB, depending on the bit depth, it becomes clear that 60 GB is enough only for installing the system and a dozen necessary programs for the operation.
If you want to burn games and heavy graphics applications like Corel or Photoshop to SSDs, consider drives with a capacity of over 120GB.
Speed
Any drive (SSD is no exception here) has two performance indicators: writing and reading. The higher the values, the better, but remember that the specifications usually indicate the maximum speed. The real meaning can only be found in practice with the help of special programs. If the drive has been on the market for a long time, then on the Internet you can try to find its speed tests from users.
Interface and form factor
Most modern SSD drives are manufactured in a 2.5 form factor with support for the SATA 3 interface. But there may be other, more expensive options:
- PCI card that plugs directly into the motherboard slot.
- External SSD storage.
- Disk with mSATA interface for installation in laptops and compact computers.
As for the interface: all new SSDs come with a SATA 3 interface, but if you have an older controller (first or second generation) installed on your motherboard, you can still connect the drive. However, there is one limitation: the baud rate is determined by the smallest value. That is, if you connect SATA 3 to SATA 2, then the speed will be determined by the SATA 2 bandwidth.
HDD for computers have a form factor of 3.5 inches, then to install an SSD 2.5 you will need a special adapter, which is often called a "sled". It is a small metal shelf that is suspended at the place where the disk is installed.
By the way, using a special adapter, you can install an SSD instead of a DVD in a laptop. Many users take out an unused drive and replace it with a solid state drive, onto which the operating system is then installed. The standard laptop hard drive is completely cleaned up at the same time and then used as storage for personal files.
Memory and controller
There are three types of memory that differ in the number of bits of information in one cell - SLC (1 bit), MLC (2 bits) and TLC (3 bits). The first type is outdated and is practically not used now, so if you see it in the characteristics, pass by such a drive.
MLC is the most common type of memory at the moment, choose it. It has its drawbacks, but there is no adequate alternative yet, since TLC is just beginning to appear on the SSD market and is still very expensive.
The situation is similar with controllers: the most popular among manufacturers and widespread among users is SandForce technology, which increases disk performance by compressing data before writing.
But SandForce controllers have one drawback, which may seem significant to someone: if the drive fills with information to the limit, then after clearing it, the write speed does not return to its original state, that is, it becomes lower. However, this problem can be solved simply: do not fill the memory to the last byte, and the speed will not drop.
There are other, more expensive options: Intel, Indilinx, Marvell. If the budget allows, it is better to look at SSDs with controllers from these companies.
Manufacturer
The last parameter that requires your attention is the manufacturer. Of course, on various forums you can find many posts about which is better to choose Kingston or, say, Silicon Power, since they specialize in the production of drives of different types.
However, this is not entirely true: there are far fewer companies that actually produce NAND flash memory than there are brands on the market. Own production (and development department) have:
- Intel.
- Samsung.
- SanDisk.
- Crucial.
OCZ, for example, did not have any developments until recently and only recently acquired the controller manufacturer Indilinx. Therefore, it is better to pay attention to the above characteristics, and keep the manufacturers in mind last.
Working with a solid state drive
After a successful purchase and successful installation of the system on an SSD, you turn on the computer and be surprised at how quickly everything started to work. To keep this agility as long as possible, follow these simple rules for using solid state drives:
- Install a system that supports the TRIM command (Windows 7 and above, Mac OS X 10.6.6, Linux 2.6.33).
- Try not to fill the disk completely - the write speed will decrease and will not recover (relevant for the SandForce controller).
- Store your personal files on the HDD. Do not remove the hard drive if it is working - store music, movies, photos and other data on it, access to which does not require high speed.
- Increase the amount of RAM and avoid using the paging file if possible.
By following these simple guidelines, you will extend the lifespan of your solid state drive and avoid premature slowdowns in its performance.
