2015/05/12 20:10:56

Solid State Drive Solid State Drive

Computer memory device based on memory chips. In addition to them, the SSD contains a control controller. Contains no moving mechanical parts.

There are two types of solid-state drives: SSD based on memory similar to computer RAM, and SSD based on flash memory.

Solid-state drives are used in compact devices: laptops, netbooks, communicators and smartphones. Some well-known manufacturers have switched to solid-state drives in full, for example, Samsung sold its hard drive business to Seagate.

SSDs are gaining popularity in the monitoring and security industry. Functions video surveillances - face recognition data analytics, solutions for "," etc. smart city- require online processing of large amounts of data. Imagine, for example, a busy intersection, the movement at which is subordinate to non-time-controlled signals, but changes dynamically depending on the traffic intensity. Cameras track the phases of decline and influx of cars and pedestrians, while calculating the most effective traffic flow parameters. This task requires a lot of computing power, and even the smallest increase in them leads to significant savings in public funds. Similar features of modern video surveillance systems give higher-performance storage devices advantages SSD over traditional hard drives (). HDD

There are also so-called hybrid hard drives, which appeared, including due to the current, proportionally higher cost of solid-state drives. Such devices combine a hard disk drive (HDD) and a relatively small solid state drive as a cache in one device (to increase the performance and life of the device, reduce power consumption). So far, such disks are used mainly in portable devices.

History of development

Chronology of events

2020: Graphene-based material to extend storage life

On January 27, 2020, it became known that an international group of scientists from NUST MISIS and the National Institute of Quantum Sciences and Radiology (Japan) developed material that will significantly increase the density of recorded information in data storage devices, such as solid-state drives and flash drives. Read more here.

2009:512 gigabyte and 1 terabyte SSD released

In 2009, Super Talent Technology released a 512 gigabyte SSD, OCZ introduces a 1 terabyte SSD. Currently, the most notable companies that are intensively developing the SSD direction in their activities are Intel, Kingston, Samsung Electronics (Samsung Electronics Rus), SanDisk, Corsair, Renice, OCZ Technology, Crucial and ADATA. In addition, Toshiba demonstrates its interest in this market.

2008: Created an SSD with a write speed of 240 MB/s and a read speed of 260 MB/s

In 2008, the South Korean company Mtron Storage Technology managed to create an SSD drive with a write speed of 240 MB/s and a read speed of 260 MB/s, which it demonstrated at an exhibition in Seoul. The volume of this drive is 128 GB. According to the company, the release of such devices will begin in 2009.

1995: First semiconductor flash drive

In 1995, the Israeli company M-Systems introduced the first semiconductor flash memory drive.

1982: Semiconductor RAM storage introduced

In 1982, the American company Cray introduced a semiconductor RAM drive for its Cray-1 supercomputers at 100 MBit/s and Cray X-MP at 320 MBit/s, 8, 16 or 32 million 64 bit words.

1978: The first semiconductor storage of the modern type was developed

In 1978, the American company StorageTek developed the first modern type semiconductor drive (based on RAM memory).

Drive to SSD

The first disks, in such a design, which became the prototype for modern drives, were created by the Scottish company Rodime, it chose the format of the then popular 3.5 floppy disks as a sample. Released in 1983, the RO351 and RO352 models had a capacity of 6.38 and 12.75 MB, respectively. At that time, this one is not so small, the original PC XT was equipped with 5-inch 5-10 MB drives, noticeably large in size. In the future, progress in the field of ferrimagnetic materials, recording methods and drives has made it possible to increase disk capacity by a million times in 25 years. The evolution of disk mechanics, materials and recording methods deserves special consideration.

However, no matter how high the capacity and capacity/price ratios of the most advanced HDDs, they remain their inherent disadvantages - a large delay as an inevitable consequence of mechanics and the sequential read and write operations inevitable when moving the head above the track.

Against expectations, the process of creating a fast electronic solid state memory (Solid State Device, SSD) was slow: it took more than a quarter of a century of experiments for the first NVM (Non-Volatile Memory) drives to appear on the market only in the late 1990s. Experiments with NAND technology, which began to be called "flash," turned out to be more successful than others. Since the early 2000s, it has firmly entered the gadget market, but only in 2013 it penetrated into corporate systems.

The duration of the NVM implementation procedure is due not so much to technical problems as to the fact that initially all modern corporate information systems were created specifically based on HDD, therefore, the inertial mass of the existing installation base became a deterrent.

Flash memory is part of a broader set of possible solutions for creating NVM, or "Storage-Class Memory SCM ,." In addition to flash memory, more than a dozen alternative physical methods fall into this category of technologies, among which the following five have advantages so far: memristors (Resistant Random Access Memory, ReRAM); Magneto-resistant Random-Access Memory (MRAM); Phase-change memory (PCM) Domain-Wall Memory (DWM) and Atomic memory. In addition to them, non-volatile static random access memory (nvSRAM) is also known; ferroelectric RAM (Ferroelectric RAM, FeRAM, or FRAM); memory based on mechanical positioning of carbon nanotubes (Nano-RAM). Of all this set, the closest are to the practical implementation of ReRAM and PCM.

The scope of SCM implementation lies between memory and disks, and since the performance and cost of technologies potentially suitable for creating SCM vary, among the solutions there may be faster, closer in performance to memory, and slower, comparable in performance to disks. Memory comparable in speed to DRAM on memristors or PCM will allow you to directly connect a large amount of memory to the processor.

Of the several ways, the most radical and logically simple involves connecting Solid State Cards (SSCs) in the PCIe form factor via the NVMe interface directly to servers, although this is the most logical and high-speed method, but it is still applicable for a limited number of new applications. Therefore, Solid State Drives with the same SSD abbreviation are widely used, available in the same form factors as HDD - 5.25, 3.5, 2.5 and 1.8 inches, emulating HDD.

Direct replacement of HDD with SDD in existing DSS acceptable, but it does not fully realize the potential of flash, so there are several options for creating new DSS. At the moment, for economic reasons, hybrid DSS systems will prevail in quantitative terms, combining the best qualities of both types of drives: both HDD and SDD - their production is growing at a rate of 8-10% per year.

In parallel, as the price of flash memory decreases, All-Flash Arrays (AFA), built exclusively on SDD, are becoming more and more massive. This segment of the market is still less hybrid, but is growing several times faster. And there are options here, too. A number of companies, mainly startups, create fundamentally new AFA class solutions from scratch (built from the ground up). The same large vendors, whose time-tested arrays retain the potential for modernization, bring their existing products by upgrading software and hardware to the AFA level. They create systems called flash optimizing storage systems (SDD). HP with 3PAR StoreServ can be cited as an example.

The advantage of AFA arrays in the built from the ground up category over optimizing storage systems is that their newly written operating systems make better use of the physical capabilities of the flash, which is obvious and unopposed. But another circumstance is no less obvious: due to the short period of existence built from the ground up, they lack the capabilities of those system tools for managing enterprise-level data (advanced data management features) that have been developed over decades for HDD. This is why serious legacy applications use these developments, without them the advantages in SDD speed are reduced to zero. It follows from this that it is impossible to compare the two types of systems described above head-on, at the moment each of them has its own advantages and the user faces the problem of choosing the DSS more precisely meets his requirements. For those who are interested in pure work speed, built from the ground up is more suitable, if the requirements of the corporate level are also critical, then optimizing storage systems is preferable, combining mature software platforms with high reliability and stability, with a higher, characteristic AFA work speed.

HDDs are not inferior to their positions, last year Western Digital introduced a 14 TB HDD using tile magnetic recording technology and hermetic zones with helium, and microwave magnetic recording (MAMR) technology is on the way, in 2022 the same WD plans to release a 40 TB disk, which will have an order of magnitude lower storage cost than SSD.

Global market

Main Article: SSD - Solid-State Drives (Global Market)

Technological progress, changes in the dynamics of the development of the PC industry, the release of new models of industrial servers and new storage architectures, as well as a short-term crisis in the hard drive market will allow the solid state storage market SSD to significantly increase in volume from 2011 to 2015.

2023: SSD manufacturers began deliberately using defective memory. Video

In mid-August 2023, information appeared that little-known Chinese manufacturers of solid-state drives, including ShineDisk, began to deliberately supply devices based on defective flash memory chips to the market. Read more here.

Russian market

Main article: SSD - Solid-state drives (Russian market)

Architecture and Operating Principle

NAND SSD

Image:220px-Disassembled HDD and SSD.JPG

Comparison: components of disassembled HDD (left) and disassembled SSD (right)

Drives built on the use of non-volatile memory (NAND SSD) have appeared relatively recently, but due to the much lower cost (from 2 dollars US per gigabyte), they began to confidently conquer the market. Until recently, they were significantly inferior to traditional drives - hard drives - in write speed, but compensated for this with a high speed of information search (initial positioning). Flash solid-state drives are already being released with read and write speeds that are many times superior to the capabilities of hard drives. They are characterized by relatively small size and low power consumption.

RAM SSD

These drives, built on the use of volatile memory (the same as used in the RAM of a personal computer), are characterized by ultra-fast reading, writing and searching for information. Their main drawback is the extremely high cost (from 80 to 800 US dollars per Gigabyte). They are used mainly to speed up the work of large database management systems and powerful graphics stations. Such drives are usually equipped with batteries to store data in case of power loss, and more expensive models are equipped with backup and/or online copying systems.

Pros and cons

Advantages over hard drives (HDDs):

absence of moving parts;
High read/write speeds, often exceeding hard drive interface throughput (SAS/SATA II 3 Gb/s, SAS/SATA III 6 Gb/s, SCSI, Fibre Channel, etc.)
low power consumption;
complete absence of noise due to absence of moving parts and cooling fans;
high mechanical resistance;
wide range of operating temperatures;
Stability of file read time regardless of location or fragmentation
small dimensions and weight;
large modernization potential of both the drives themselves and their production technologies.
much less sensitivity to external electromagnetic fields.

Shortcomings

The main drawback of SSDs is the limited number of rewriting cycles. Regular (MLC, Multi-level cell, multi-level memory cells) flash memory allows you to write data about 10,000 times. More expensive types of memory (SLC, Single-level cell, single-level memory cells) - more than 100,000 times. Load balancing schemes are used to combat uneven wear. The controller stores information about how many times which blocks have been rewritten and, if necessary, "swap them";
A problem with the compatibility of SSD drives with outdated and even many current versions of the OS family, Microsoft Windows which do not take into account the specifics of SSD drives and further wear them out. The use of the swap mechanism on the SSD by operating systems also, with a high probability, reduces the life of the drive;
The price of a gigabyte of SSDs is significantly higher than the price of a gigabyte of HDD. In addition, the cost of SSDs is directly proportional to their capacity, while the cost of traditional hard drives depends on the number of plates and grows more slowly as the storage volume increases.

Temperature dependence of storage time on de-energized SSDs

On May 12, 2015, it became known about the publication of a report by Alvin Cox, head of Seagate and chairman of the JEDEC (Joint Electron Device Engineering Council) committee^[1] report], he outlined the features of a new standard that defines the requirements for SSDs based on the NAND memory platform and methods for assessing their reliability^[2].

The text of the report reports on the limited time for saving data when the SSD-drive is disconnected from the power supply:

for server devices, the guaranteed time of autonomous storage of all data is determined in three months at a temperature of 40 ° С,
for client systems - 1 year at a temperature of 30 ° С.

Table shows correspondence of temperature/storage time in de-energized state, 2015

The report also states that according to research by Samsung, Seagate and Intel, the period of time for storing data is halved when the temperature of the place where the SSD is stored increases for every 5 ° C. For example, at a temperature of 55 ° C, the time for storing all data while the drive is offline decreases to a week.

Storage Utilization: Practice Lags Behind Theory

The experience of recycling HDD drives without taking into account the features of SSDs is widespread on the market. Incorrect disposal can lead to a data breach. An audit conducted in the United States in 2015 showed that incorrect methods of erasing files led to the leakage of personal information of citizens from the databases of 12 American departments, including tax and health care^[3].

According to Verizon's Data Breach Investigation Report, published at the end of April 2016, 86% of attempts to steal confidential data are attempts to seize financial information. From this point of view, corporate DSS drives are an ideal source of other people's data, because when deleting files, information on disks does not actually disappear.

End-of-life HDD disposal technology has already been worked out: demagnetization reliably erases all data. For SSDs, demagnetization does not work. Therefore, some companies choose the physical destruction of SSDs - as a result, the hammer becomes the best friend of the system administrator. However, this approach cannot be called optimal, because the re-sale or processing of a valuable device is more profitable in terms of ecology and partial reimbursement of the cost.

SSD Rules

Cryptographic erasure is mandatory when disposing of corporate SSDs. This process involves changing the key that is used to encrypt and decrypt data. As a result, it is almost impossible to restore data on a "disinfected" medium. This procedure shall be performed only by qualified specialists. In this case, the erase procedure report should contain exact information about who performed the procedure, the name, serial number of the drive, etc. Attackers often try to fake such reports, so the corresponding logs on the execution of all the procedures listed in the report must be attached to the report.

The disinfection procedure should be carried out even if it is decided to send the drives for recycling. Thus, SSD utilization is no more difficult than HDD utilization, you just need to take into account the technological features of the next generation carrier.

Business application migration to SSD

Moving the data of the most performance-demanding business applications to an SSD is justified in many cases. The performance growth achieved by SSDs is often more efficient than the traditional increase in the number of conventional hard drives in the storage system.

Total cost of ownership (TCO) is improved by reducing air conditioning and power costs. The array is more compact and able to handle more transactions. But if the cost of processing one transaction in such a system is quite low, then the price per gigabyte of storage remains very significant. Flash drives are still very expensive, and this limits the ability to migrate business applications to SSDs.

At the same time, a number of problems remain for the equipment of most vendors. Firstly, this is non-standard equipment that is technologically not fully compatible with what is already available. The second problem is the wear of drives. It is known that the number of SSD rewriting cycles is limited, and as you use it, the risk of data loss increases. The third problem is the limited functions of the controller software in terms of integration, data compression and support for network protocols.

There is a high-quality alternative from HP - a specialized HP 3PAR 7450 array, which runs a standard set of 3PAR OS software. It is a storage system with increased controller performance that can handle up to 900,000 I/O per second with a response time of less than 0.7 milliseconds, and a bandwidth of up to 5.2 GB/s. HP 3PAR 7450 is able to "pack" information with a coefficient from 4:1 to 10:1, depending on the load profile and the nature of the data. The hardware implementation allows not only to increase the efficiency of disk space use, but also to evenly distribute the load and prevent excessive wear of the SSD.

In traditional hard disk arrays, read operations are relatively slow and data is cached in large blocks of 16 KB. This increases the chances that the next read operation will already occur from the cache, thereby reducing the response time. SSDs are much faster, and it makes no sense to pre-move data to the cache when using them.

At the same time, HP guarantees the reliability of four-controller HP 3PAR StoreServ at 99.9999% data availability. This means that the idle time of the array will be no more than 31.5 seconds per year, or 2.59 per month, or 0.605 seconds per week.

Use on Apple and PCs

Microsoft Windows and this platform's computers with SSDs

Windows 7 introduced special optimization for working with solid-state drives. With SSDs, this operating system works differently with them than with conventional HDDs. For example, Windows 7 does not apply defragmentation, Superfetch and ReadyBoost technologies and other proactive read techniques to an SSD disk that speed up loading applications from regular HDD drives.

Previous versions of Microsoft Windows do not have such special optimization and are designed to work only with ordinary hard drives. Therefore, for example, some Windows Vista file operations, without being disabled, can reduce the life of the SSD. The defragmentation operation should be disabled, as it has practically no effect on the performance of the SSD and only further wears it out.

ASUS Back in 2007, the company released the EEE PC 701 netbook with a 4GB SSD. On September 9, 2011, Dell announced the first in the market for Dell Precision laptops with 512GB solid-state memory with one drive and 1TB with two drives for M4600 and M6600 computers, respectively. The manufacturer set the price for one 512GB SATA3 drive at the time of announcement at $1,120 dollars.

The SSD drive is powered by Acer tablets - Iconia Tab W500 and W501, Fujitsu Stylistic Q550 models running Windows 7.

Mac OS X and Macintosh Computers with Solid State Drives

The Mac OS X operating system, starting with version 10.7 (Lion), fully provides TRIM support for the solid state memory installed on the system.

Since 2010, Apple has introduced the Air line of computers fully equipped with only solid-state memory based on Flash-NAND memory. Until 2010, the buyer could choose a regular hard drive for this computer in the package, but the further development of the line in favor of maximum ease and reduction of the case of computers of this series required a complete abandonment of ordinary hard drives in favor of solid-state drives. The amount of memory in the Air series computers ranges from 64GB to 512GB. According to J.P. Morgan, 420,000 computers of this series have been sold entirely on solid-state Flash-NAND memory since presentation.

Notes

↑ [http://www.jedec.org/sites/default/files/Alvin_Cox%20%5BCompatibility%20Mode%5D_0.pdf. In the JEDEC SSD Specifications Explained
↑ Dependence of storage time on de-energized SSDs on temperature
↑ Companies lose valuable data without being able to dispose of SSDs