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1. SOLID STATE DRIVES EXPLAINEDgo backSolid state drives (SSDs) use solid state flash memory, instead of the spinning magnetic platter used by traditional hard disk drives (HDDs). For many applications, therefore, SSDs possess a number of unique characteristics which provide advantages compared to HDDs. Below is a table listing the major desirable characteristics of SSDs, as well as some example applications where these characteristics can be useful. 2. SSD ADVANTAGESgo back
3. CHOOSING THE RIGHT SSD TECHNOLOGY (MLC versus SLC)go backThere are two types of NAND flash memory used to construct SSDs: Multi Level Cell (MLC) - a flash memory technology using multiple levels per cell to allow more bits to be stored. MLC NAND has the benefit of being cheaper due to the denser storage method used, but software complexity can be increased to compensate for a larger bit error ratio. Single Level Cell (SLC) - stores data in individual memory cells, which are made of floating-gate transistors. SLC memory has the advantage of faster write speeds, lower power consumption and higher cell endurance (generally 10x that of MLC). However, because it stores less data per cell, it costs more per megabyte of storage to manufacture Typically, industrial applications will favour SLC flash (high performance, higher cost), while non-industrial applications will favour MLC (standard performance, lower cost).
4. WRITE CYCLE LIMITATION EXPLAINEDgo backDue to the nature of NAND technology it is fairly easy to calculate the expectable length of life of SSDs, opposed to HDD, where it is hard to predict material wear out of components. Most MLC based NAND-Flash SSD will feature 5.000 to 10.000 full write cycles and SLC based NAND-Flash SSD feature some 100.000 full write cycles, before about 3 % of the flash memory will show signs of instability, causing a potential failure of the entire SSD. The wear out of SSD is only affected by write cycles and a virtual unlimited amount of reads can be done to the NAND flash. For most applications the ration is about 20% write and 80% read. For most this sounds like a significant limitation, but in reality most SSDs will last 3-5 times as long as the most durable HDDs today. 5. LIFETIME PREDICTION MODELSgo backThe most commonly used lifetime prediction models is:
Endurance Rating x GB of Storage x (0.0325)
Lifetime = ----------------------------------------------------------------------------
Maximum write speed (MB/s) x Duty Cycle x (Hours of usage per day/ 24)
Where:
5.1 EXAMPLE:go backPhotofast G-Monster V5 MLC 256GB drive, with 10k full write cycles and a rated write speed of 270 MB/s used 8 hours per day with 20% of that time for writing files, will last:
(10) x 256 x (.0325)
Lifetime = ----------------------- = 4.6 years
270 x 0.2 x 8/24
Note: this model does not take into account
A more sophisticated model, taking into account various file block sizes, is:
Endurance Rating x GB of Storage x (0.0325) * 1024
Lifetime = ---------------------------------------------------------------------------
Write IOPS Rating x File Size in KB x Write Amplification x Duty Cycle
Where:
Write Amplification - a factor mostly kept at secret by manufacturers and will range between 2 and up to 30 or more depending on the quality of the flash memory and data allocation algorithms used. Duty Cycle - expect write usage of the SSD (for example 20% writing and 80% reading) 5.2 EXAMPLE:go backPhotofast G-Monster V4s SLC 128GB drive, with a write amplification factor of 10, and 6000 IOPS at 4k block size used in a 24h per day operating database server, with a estimated duty cycle of 20% write and 80% read and a written data block size of 4k will last:
(100) x 128 x (.0325) x 1024
Lifetime = ------------------------------ = 8.87 years (at 24h x 365 days work)
6000 x 4 x 10 x 0.2
6. THE RELATIONSHIP BETWEEN BRAND NAME, PRICE AND QUALITYgo backAs a surprise to most SSDs are not a commodity product, nor is a well known brand automatically a guarantee for highest reliability and performance. The reason, as indicated in the formulas above, are:
Generally there is a high correlation between price, quality and performance and "economic" Solid State Drives are generally more likely to fail, commonly due to a very high write amplification number and cheap transistors used, even if the SSD is from a well-known brand. Hence an economic SSD can be attractive to a general user for running day-to-day office applications, yet a professional user should definitely consider higher grade SSDs. There are many online publications comparing Products in the market and here at SSDEurope we are always happy to provide our recommendations. Just post your question to: info@SSDEurope.com  for all brands we offer
7. PERFORMANCEgo backThere are several factors which need to be taken into account when evaluating the performance of an individual SSD. The stability of performance is most commonly determined by:
7.1 Maximum read/write performancego backMostly a theoretical value for blocks of data between 1MB-50 MB of data, generally not achieved by most users in real life applications 7.2 Sustained read/write performancego backA value showing the performance of the SSD when file sizes read/written are constantly increasing (for example: HD video recording). NOTE: most "economic" SSDs will demonstrate a significant drop in performance and stuttering issues when larger than 50MB file sizes are written/ read 7.3 IOPSIOPS (Input/output Operations Per Second) is a common benchmark for Hard Disks and other computer storage media and shows the throughput ability of various block sizes. Programs such as IOMeter, IOZone, CrystalDiskMark or HDTune are used to determine IOPS numbers. A standard 7200 RPM HDD will be able to handle 4k data blocks at around 120 IOPS Economic SSD will handle 4k data blocks at about 1600 IOPS Sophisticated SSDs will handle 4k data blocks at 8000-30.000 or more IOPS The effect of IOPS numbers is generally highly correlated to the time needed to load programs, such as operating systems, databases and other applications. - to compare all the different SSDs according to their performance
8. EXAMPLE APPLICATIONS OF SSDgo back8.1 General usersgo back
- to order your Solid State Drive
8.2 Video/ Broadcasting industrygo back
- to order your Solid State Drive
8.3 Engineering & Designgo back
- to order your Solid State Drive
8.4 Network Access Storage (NAS), Storage Area Network (SAN) & Supercomputinggo back
- to order your Solid State Drive
8.5 Oil & Gas and Military applicationsgo back
- to order your Solid State Drive
8.6 CCTV & mobile surveillancego back
- to order your Solid State Drive
8.7 Harsh environmentsgo back
- to order your Solid State Drive
9. Solid State Drives (SSD) versus Hard Disk Drives (HDDs)go backComparing SSDs against HDDs is somewhat of a tricky task. First of all there are technical differences, such as the method of data storage and data retrieval. Then there are performance differences among different HDDs and SSDs. And finally there is the issue about price and benefits. Below we will try to address some of the most prominent differences. 10. Lifespan differencesgo backThe first noticeable physical difference is that HDDs consist of rotating, magnetically coated disks, known as platters, that are used to store data. This rotating motion of the mechanical arms results in much wear and tear after long periods of use. The rated operational lifespan of a computer HDD is typically over three years, yet shock, vibration, high humidity levels and temperature fluctuations can result in the famous “click of death”, a clicking noise indicating that the HDD is physically damaged. Although the most common Flash chips have around 300,000 write cycles, the best Flash chips are rated at 1,000,000 write cycles per block. On top of that, Flash SSD manufacturers employ different ways to increase the longevity of the drives. In some cases, they use a "balancing" algorithm to monitor the number of times each disk block has been written, which greatly extends the operational lifespan of the drive. Furthermore, these manufacturers also designed special "wear-leveling" algorithms where once a certain percentage threshold for a given block is reached, the SSD controller will swap the data in that block with the data in another block that has exhibited a "read-only-like" characteristic in the background. This reduces performance lag and avoids further wearing off of the blocks and thrashing of the disk. Even with usage patterns of writing/reading gigabytes per day, a Flash-based SSD should last several years, depending on its capacity. Add to that the inclusion of a DRAM cache in the disk architecture that further enhances its operational capabilities as well as lifespan. 11. Performance differencesgo backWith the very fast paced lifestyle these days, most businesses are time-bound and cannot afford a slowing down in their transactions. This makes speed of HDDs a crucial point in technological purchases. The typical access time for a Flash based SSD is about 35 - 100 micro-seconds, whereas that of a rotating disk is around 5,000 - 10,000 micro-seconds. That makes a Flash-based SSD approximately 100 times faster than a rotating disk. Access times are not the only performance difference. Most HDDs and SSDs are rated at sustained read and write speeds, which normally would address the data-transfer speed of uncompressed / unfragmented files such as uncompressed HD video or uncompressed photographs. Yet in most applications data is highly fragmented and stored in block of data of various sizes in various locations on the HDD/SSD. Today most HDDs are actually limiting the potential of a computer system since they are not able to keep up with the performance of the other components, particularly the CPU. The key performance difference between HDDs and SSDs is the read/write speed of small block of data. Generally a standard 7200 RPM HDD reaches 60 MB/s sustained read/write performance of uncompressed data and a typical SSD some 200 MB/s sustained read/write performance (or 3 x times as fast), yet when fragmented data of small block sizes (4k, 8k) is written, such as in SQL databases or your standard Operating System (WIN 7, MAC OS) a HDD will struggle to reach 0.4 MB/s read/write whereas even the most economic SSD will easily reach 10 MB/s or more. The benchmark results below clearly show these differences: - for our high performance SSDs
11.1 The benchmark results below clearly show the performance difference:go back
Differences in performance stability are shown below:
A great video from Samsung further demonstrates the differences between a mid-class Samsung SSD and a standard HDD: Finally HDDs performance is the best when much free capacity is still available and outer tracks on the platters are written on. The fuller the HDD gets the more data is normally written on inner tracks and therefore less data can be read/written per rotation of the platter, due to the smaller length of the inner tracks. SSDs tend to maintain the same performance no matter how much capacity ins being used and hence defragmentation is not needed for SSDs. 12. Reliabilitygo backIn terms of reliability, conventional HDDs pale when compared to SSDs. The absence of mechanical arms and spinning platters is the reason behind its reliability. In demanding environments, SSDs provide the type of ruggedness required for mobile applications. Unlike the HDD, SSD's can withstand extreme shock and vibration with data integrity and without any danger of data loss. This feature is very important in industrial applications where exposure to highly combustible materials and electromagnetic radiation are typical. Their ability to deliver unnerving performance in extreme conditions also makes SSD play a vital role in military operations, be it in defence, aerospace or aviation applications. Military applications require, in most cases, an operating temperature range of -60°C to +95°C. Shock, vibration, and temperature ratings of HDDs cannot comply with military standards, only SSDs can. 13. Cost comparison between HDD, SSD and DRAMgo backIn this section we will provide a cost/ benefit analysis between HDDs, SSDs and DRAM solutions and secondly analyse the cost differences between various SSDs.
From the table the following is evident: 1. HDDs have the lowest Cost/ GB and hence are good for pure data storage / archiving 2. DRAM Solutions have the lowest Cost/ IOPS ration and are ideal for storage solution which require very fast access speeds 3. SSD provide a great intermediate solution, effectively addressing the disadvantages of HDDs (performance & reliability) and the disadvantages of DRAM (very high per GB cost).
14. Cost differences among SSDsgo backThe price of SSDs is generally derived from the following factors: Cost of Flash grade used
Components used
Assembly quality
Sophistication of inbuilt programs
In-Built cache – DRAM
Let’s compare 2 very reliable SSDs
Generally there is a high correlation between price, reliability and performance. In the example above 2 times the price could provide 3 times the performance. In the world of SSDs well known brand names do not necessarily indicate high reliability or performance. We experienced up to 30% failure rates within the first 5 months with some well known manufacturers and less than 1% failure rates with some less known brands. The reasons are often a bit technical and there is often no one straight answer to what works and what not. Please be guided by professional reviews and if in doubt our team will gladly assist to identify the best solution for you taking into account your budget and performance needs. |
