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PROCESSOR TYPES (CONT’D)
Every consumer SSD company has adapted SandForce processors into their SSD family except Samsung and Intel although there is evidence that Samsung will soon release a 520 Series SSD for enthusiasts which contains the SandForce SF-2281 processor.
The other family of processors are those that do not use compression and are common in processors manufactured by Marvell, Intel, Samsung, and some lesser known names such as JMicron and Phison. The below picture is of a Crucial M4 512GB SATA 3 SSD which utilizes the Marvell 9174 controller.
Marvell processors have gained most of their success through Crucial/Micron although Intel, Corsair, and many other manufacturers have relied in them as well.
NAND FLASH MEMORY
The sole purpose of NAND flash memory is to provide storage for your data somewhat similar to that of the magnetic disk of a hard drive. In the Crucial 512GB we see above, there are 16 memory modules of 32GB capacity each for a total of 512GB. Typically, all SSDs are normally advertised in capacities that directly reflect the memory module itself which traditionally is a power of 4. A single module could have been as low as 4GB where now they can reach 64GB. This is why we would normally see 32, 64, 128, 256, 512GB SSDs advertised although manufacturers such as Intel have ventured off the beaten path to advertise capacities of 320GB as we saw in our review of the Intel 320 Series 300GB SATA 2 SSD.
Performance of non-compressed SSDs can also be affected by the number of die within the memory which is the reason that we see different performance specifications for different capacity drives. This was initially very visible in the Intel X25m 160GB SSD which was an excellent SSD although its maximum write speeds was limited to just over 100MB/s transfer speed.
SANDFORCE SSD CAPACITIES
“SandForce Driven” SSDs can easily be spotted as their drive capacity goes against the grain. Whereas we spoke of capacities of 32, 64, 128, 256 and 512GB above, companies that utilize SandForce SSDs have their product advertised in capacities that are typically 30, 60, 120, 240, and 480GB. This is because SandForce is able to improve the performance and lifespan of their product through their firmware and over provisioning, over provisioning which typically steals away 7% of NAND flash memory for the consumer and as high as 28% for enterprise.
OVER PROVISIONING AND DRAM CACHE MEMORY
When SSDs were first introduced to the consumer, capacity was a very limiting factor and people soon realized that SSD performance slows significantly when it approaches being full. Fortunately, there had been a great deal of advance which has relieved this performance decline, for the most part and it comes by way of a DRAM cache for non-compressed drives. We see cache modules in use by Intel, Samsung, Crucial and others that use Marvell, JMicron and Phison controllers.
This pictures shows the Hynix DDR3-1333 SDRAM 128MB cache on the Intel 510 SSD.
SandForce does not use a cache as it takes control of that 7/28% over provisioning for just that purpose and it’s end result is sustained performance and a longer lifespan overall.
To show how really advanced SSDs and their technology has become, a ‘SandForce Driven’ SSD is able to monitor itself and if a cell/page/block of memory were to fail, the firmware actually recognizes this and swaps the information to a portion of the over provisioning where it is then remapped. Unlike a hard drive which will lose some capacity and scream corrupted cells, the SSD user would never have knowledge of the repair and the SSD would not suffer any loss of capacity.
I guess it’s safe to assume you’ll be covering in more detail how the die sizes, process shrinks and empty/unused controller channels make for slower and slower small drives and eventually may end up requiring you to buy a 512gb drive of some models (cough-Octane-cough) just to get the max performance. I even came across an article that predicts that SSDs will ultimately commit slow suicide with the continuing die shinks and resulting lower and lower write speeds.
I’ve answered TONS of posts on Ocz’s forums from users who don’t understand why their 60GB V3 is so slow vs a 120 or 240…and TWICE as many who don’t understand the write penalty with incompressible data on a SF controller and proceed to post an as_ssd or CDM screeny asking where the specd 500reads/500writes are.
Oh speaking of process shrinks…if anyone is in the market for a 34nm toggle equipped SF2200 (i.e. Ocz MaxIOPs) you better get ’em while you can…transition to 24nm toggle is upon us. Similar to the 32nm to 25nm transition, write speeds will take a hit as well as the base durability (P/E cycles) even tho it will bring the price down further…but I’m the type who doesn’t mind paying a little extra for the faster writing drive with more durable nand.
p.s. My message above suddenly disappeared (??)
MRFS
Thanks, Les.
I think your entire website would benefit enormously by expanding your working definition of “solid-state”.
Clearly, the IT world has more or less adopted “SSD” as the preferred acronym for memory devices that utilize one of several variants of Nand Flash e.g. MLC and SLC in different die sizes, different controllers and varying capacities with or without internal DRAM cache.
However, a ramdisk that utilizes SDRAM to emulate a file system partition would also qualify as a “solid-state” memory technology.
This latter approach to accelerating the speed of most recently used “working sets” has taken on added important with the release of chipsets that support 6 and now 8 DIMM slots e.g. Intel’s X79 chipset with quad-channel memory access.
See our “Technical Review and Evaluation of RamDisk Plus Software”.
KEEP UP THE GOOD WORK!
MRFS
Hopefully the issues with SSD failures, BSOD, lost data, compatibility and reliability issues will be discussed for those who are unaware that consumer grade SSDs are “immature tech” and a potential liability for anyone who needs secure data.
Sounds like your referring pretty much to SF’s teething pains…hardly representative of the entire SSD industry. SSDs are no worse than HDD failure rates btw…
Typo on the beginning of page 2, you wrote Samsung will release a 520 with SF controller, but I know you meant Intel.
Thanks Les now I need to find the buyers at the factories. I have a whole bunch of Flash that I want to sell. mhayward@t-online.demhayward@t-online.de
I just got a SSD, it came with it’s own transfer software. For some reason it did not work very well. so I went to my old standby ACRONIS. I treated the SSD as the same way I would any other drive. I used Widow’s partition manger to set it up, works fine. Also I purchased a UPS power supply to protect the SSD from power frailer, there cheep and will protect your equipment.