Subject: Storage, Shows and Expos | September 16, 2014 - 11:29 AM | Allyn Malventano
Tagged: ssd, slc, sata, mlc, micron, M600, crucial
You may already be familiar with the Micron Crucial M550 line of SSDs (if not, familiarize yourself with our full capacity roundup here). Today Micron is pushing their tech further by releasing a new M600 line. The M600's are the first full lineup from Micron to use their 16nm flash (previously only in their MX100 line). Aside from the die shrink, Micron has addressed the glaring issue we noted in our M550 review - that issue being the sharp falloff in write speeds in lower capacities of that line. Their solution is rather innovative, to say the least.
Recall the Samsung 840 EVO's 'TurboWrite' cache, which gave that drive a burst of write speed during short sustained write periods. The 840 EVO accomplished this by each TLC die having a small SLC section of flash memory. All data written passed through this cache, and once full (a few GB, varying with drive capacity), write speed slowed to TLC levels until the host system stopped writing for long enough for the SSD to flush the cached data from SLC to TLC.
The Micron M600 SSD in 2.5" SATA, MSATA, and M.2 form factors.
Micron flips the 'typical' concept of caching methods on its head. It does employ two different types of flash writing (SLC and MLC), but the first big difference is that the SLC is not really cache at all - not in the traditional sense, at least. The M600 controller, coupled with some changes made to Micron's 16nm flash, is able to dynamically change the mode of each flash memory die *on the fly*. For example, the M600 can place most of the individual 16GB (MLC) dies into SLC mode when the SSD is empty. This halves the capacity of each die, but with the added benefit of much faster and more power efficient writes. This means the M600 would really perform more like an SLC-only SSD so long as it was kept less than half full.
As you fill the SSD towards (and beyond) half capacity, the controller incrementally clears the SLC-written data, moving that data onto dies configured to MLC mode. Once empty, the SLC die is switched over to MLC mode, effectively clearing more flash area for the increasing amount of user data to be stored on the SSD. This process repeats over time as the drive is filled, meaning you will see less SLC area available for accelerated writing (see chart above). Writing to the SLC area is also advantageous in mobile devices, as those writes not only occur more quickly, they consume less power in the process:
For those worst case / power user scenarios, here is a graph of what a sustained sequential write to the entire drive area would look like:
Realize this is not typical usage, but if it happened, you would see SLC speeds for the first ~45% of the drive, followed by MLC speeds for another 10%. After the 65% point, the drive is forced to initiate the process of clearing SLC and flipping dies over to MLC, doing so while the host write is still in progress, and therefore resulting in the relatively slow write speed (~50 MB/sec) seen above. Realize that in normal use (i.e. not filling the entire drive at full speed in one go), garbage collection would be able to rearrange data in the background during idle time, meaning write speeds should be near full SLC speed for the majority of the time. Even with the SSD nearly full, there should be at least a few GB of SLC-mode flash available for short bursts of SLC speed writes.
This caching has enabled some increased specs over the prior generation models:
Note the differences in write speeds, particularly in the lower capacity models. The 128GB M550 was limited to 190MB/sec, while the M600 can write at 400MB/sec in SLC mode (which is where it should sit most of the time).
We'll be testing the M600 shortly and will come back with a full evaluation of the SSD as a whole and more specifically how it handles this new tech under real usage scenarios.
Subject: Storage | July 26, 2013 - 03:08 PM | Jeremy Hellstrom
Tagged: TurboWrite, tlc, ssd, slc, Samsung, 840 evo, MEX controller
Along with Al's review of the new EVO line you can get a second opinion from The Tech Report about the performance of the new SSD with a fast cache. The majority of the storage is 19nm TLC NAND but there is an SLC cache sitting between the controller and that long term TLC storage to help with the overall responsiveness of the drive, aka TurboWrite. In the 120 and 250GB models that cache is 3GB while in the larger models you get a 6GB cache. In their real world testing the new EVO drive is incredible at large file copying though Sandforce drives can beat it in small file copy speeds, likely thanks to the compressed write trickery that controller family is so good at. Check out the review here and keep your fingers crossed that MSRP is the acual price these drives sell at.
"Samsung's entry-level 840 EVO SSD combines affordable TLC NAND with a server-style SLC cache. We explain the drive's unique buffering tech and explore how it affects performance."
Here are some more Storage reviews from around the web:
- Samsung 840 EVO SSD @ The SSD Review
- Samsung SSD 840 EVO Review: 120GB, 250GB, 500GB, 750GB & 1TB Models Tested @ AnandTech
- Samsung 840 EVO 250GB, 750GB SSD Review @ Custom PC Review
- Samsung 840 Evo SSD @ Hardware.info
- Samsung unveils 840 EVO solid-state drive family @ The Tech Report
- 240GB OCZ Vertex 450 Solid State Drive @ Benchmark Reviews
- Plextor M5M 128GB mSATA SSD Review @ Legit Reviews
- OCZ Vertex 3.20 240GB SSD @ eTeknix
- OCZ Vector 512GB SSD @ Kitguru
- RunCore Pro IV 1.8 Inch ZIF SSD @ LanOC Reviews
- Silicon-Power Velox V55 240GB @ Legion Hardware
- Seagate 600 Pro SSD 400GB @ Bjorn3D
- Securely Erasing Your SSD with Linux: A How-To @ Techgage
- Seagate Central 3TB review: User-friendly? @ Hardware.info
- Silicon Power Blaze B20 32GB USB 3.0 Flash Drive @ NikKTech
- USB 3.0 Flash Drive Roundup July 2013 @ Legion Hardware
- Icy Dock FlexCage 2 Bay and 3 Bay Hard Drive Enclosure Review @ HiTech Legion
- Zalman ZM-VE400 USB 3.0 HDD/SSD Enclosure @ Funky Kit
- QNAP TS-421 & QTS 4.0 @ techPowerUp
- Thecus N2520 review: first NAS with Intel Atom CE5315 @ Hardware.info
Introduction and Specifications
Last week, Samsung flew a select group of press out to Seoul, Korea. The event was the 2013 Samsung Global SSD Summit. Here we saw the launch of a new consumer SSD, the 840 EVO:
This new SSD aims to replace the older 840 (non-Pro) model with one that is considerably more competitive. Let's just right into the specs:
Subject: Storage | July 17, 2013 - 10:12 PM | Allyn Malventano
Tagged: tlc, ssd, slc, sata, Samsung, cache, 840 evo
Samsung's release of the 840 EVO earlier today likely prompted some questions, such as what type of flash does it employ and how does it achieve such high write speeds. Here is the short answer, with many slides in-between, starting off with the main differences between the 840 and the 840 EVO:
So, slightly increased specs to help boost drive performance, and an important tidbit in that the new SSD does in fact keep TLC flash. Now a closer look at the increased write specs:
Ok, the speeds are much quicker, even though the flash is still TLC and even on a smaller process. How does it pull off this trick? Tech that Samsung calls TurboWrite.
A segment of the TLC flash is accessed by the controller as if it were SLC flash. This section of flash can be accessed (especially written) much faster. Writes are initially dumped to this area and that data is later moved over to the TLC area. This happenes as it would in a normal write-back cache - either during idle states or once the cache becomes full, which is what would happen during a sustained maximum speed write operation that is larger than the cache capacity. Here is the net effect with the cache in use and also when the cache becomes full:
For most users, even the smallest cache capacity will be sufficient for the vast majority of typical use. Larger caches appear in larger capacities, further improving performance under periods of large write demand. Here's the full spread of cache sizes per capacity point:
So there you have it, Samsung's new TurboWrite technology in a nutshell. More to follow (along with a performance review coming in the next few days). Stay tuned!
Subject: Storage | July 15, 2013 - 01:05 PM | Jeremy Hellstrom
Tagged: sandisk, Extreme II series, ssd, mlc, slc
SanDisk has done something interesting with their new Extreme II SSD series, they have used both SLC and MLC flash in the drive to attempt to give users the best of both worlds. The drive still has a DDR cache sitting between the flash storage and the controller, but there is an nCache between the MLC flash and the DDR comprised of ~1GB of SLC flash. The idea is that the SLC can quickly accumulate a number of small writes into a larger single write block which can then be passed to the MLC flash for storage. Don't think of it as a traditional cache in which entire programs are stored for quick access but more as a write buffer which fills up and then passes its self to the long term storage media once it is full. The Tech Report put this drive through their tests and found it to be a great all around performer, not the fastest nor the best value but very good in almost any usage scenario.
"With MLC main storage and an SLC flash cache, the SanDisk Extreme II is unlike any other SSD we've encountered. We explore the drive's unique design and see whether it can keep up with the fastest SSDs on the market."
Here are some more Storage reviews from around the web:
- Corsair Neutron GTX 240GB SSD RAID 0 Performance @ Legit Reviews
- SanDisk Extreme II @ SSD Review
- OCZ Vector 256GB @ LanOC Reviews
- Silicon Power Velox V55 240GB SSD @ NikKTech
- Western Digital Se 4TB Review @ TechwareLabs
- Seagate Laptop Thin SSHD 500 GB HDD Review @ Hardware Secrets
- Seagate Desktop HDD.15 4TB / Barracuda XT 4TB @ Hardware.info
- Western Digital SE 4TB Hard Drive @ hardCOREware
- Toshiba Nearline MG03ACA400 4TB SATA III HDD @ NikKTech
- Western Digital Sentinel DX4000 16TB RAID5 4-Bay NAS @ eTeknix
- Icy Box IB-WF200HD @ Rbmods
- Sandisk Extreme microSDXC UHS-I 64GB Memory Card Review @ Legit Reviews
- Patriot SuperSonic Mini 16GB USB 3.0 Flash Drive @ NikKTech
- 49 SD and MicroSD cards tested: there's a difference @ Hardware.info
- Mach Xtreme MX-FX 32GB USB 3.0 Flash Drive @ NikKTech
Subject: Storage | March 28, 2013 - 01:15 PM | Jeremy Hellstrom
Tagged: SuperSSpeed, S301 Hyper Gold, ssd, slc, SandForce SF-2281
SuperSSpeed is mixing the performance and endurance of SLC flash storage with the lower cost of the SandForce SF-2281 in an attempt to bring the price of their SLC drive to an affordable level for the consumer. The mix seems a good idea as the reduced write latency of SLC flash may help to overcome SandForce's weakness when writing incompressible data. [H]ard|OCP's testing bears this out as the drive kept up with a larger Samsung 840 Pro, one of the current performance kings. You will pay for the privilege however as the 128GB drive currently retails for $250 as SLC flash is not cheap. Consider that in almost any casual usage scenario, you are never going to push this drive to its limits ... unless you are going to start your own Frame Rating machine.
"The SuperSSpeed S301 128GB SLC SSD brings SLC flash into the consumer market. The extreme endurance and excellent write performance makes for an interesting SSD powered by the SandForce SF-2281 controller. The Intel 25nm SLC NAND removes much of the Achilles heel of the SandForce processors, delivering consistent performance."
Here are some more Storage reviews from around the web:
- OCZ Vertex 3.20 – Vertex 3 updated to 20nm @ Bjorn3D
- OCZ Vertex 3.20 120GB Solid State Drive Review @ Pro-Clockers
- OCZ Vertex 3 .20 120GB SSD @ Tweaktown
- OCZ Vertex 3 .20 240GB SSD @ Tweaktown
- KingFast Ultra-Cache K13 & K25 SATA2 SSD Review @ ModSynergy
- Kingston V300 120GB SSD Review @ HCW
- Kingston V300 120GB SSD @ Bjorn3D
- Intel 335 Series 180GB SSD Review @ Hardware Canucks
- The SSD Review SSD Database Is Live
- ADATA DashDrive Air AE400 Wireless Storage Device @ Tweaktown
- Kingston DataTraveller Ultimate 3.0 G3 64GB USB3.0 Flash Drive @ Tweaktown
- Kingston HyperX Predator 512GB USB 3.0 Flash Drive @ Tweaktown
- QNAP TS-469L @ Legion Hardware
- G-Technology G-Drive Mobile USB 1TB USB 3.0 Portable Hard Drive Review @ NikKTech
- OWC Mercury On-The-Go Pro USB 3.0 Portable Enclosure Kit Review @ Madshrimps
- ADATA DashDrive HV610 External Hard Drive @ Tweaktown
- ADATA DashDrive Durable HD710 External Hard Drive @ Tweaktown
Taking an Accurate Look at SSD Write Endurance
Last year, I posted a rebuttal to a paper describing the future of flash memory as ‘bleak’. The paper went through great (and convoluted) lengths to paint a tragic picture of flash memory endurance moving forward. Yesterday a newer paper hit Slashdot – this one doing just the opposite, and going as far as to assume production flash memory handling up to 1 Million erase cycles. You’d think that since I’m constantly pushing flash memory as a viable, reliable, and super-fast successor to Hard Disks (aka 'Spinning Rust'), that I’d just sit back on this one and let it fly. After all, it helps make my argument! Well, I can’t, because if there are errors published on a topic so important to me, it’s in the interest of journalistic integrity that I must now post an equal and opposite rebuttal to this one – even if it works against my case.
First I’m going to invite you to read through the paper in question. After doing so, I’m now going to pick it apart. Unfortunately I’m crunched for time today, so I’m going to reduce my dissertation into the form of some simple bulleted points:
- Max data write speed did not take into account 8/10 encoding, meaning 6Gb/sec = 600MB/sec, not 750MB/sec.
- The flash *page* size (8KB) and block sizes (2MB) chosen more closely resemble that of MLC parts (not SLC – see below for why this is important).
- The paper makes no reference to Write Amplification.
Perhaps the most glaring and significant is that all of the formulas, while correct, fail to consider the most important factor when dealing with flash memory writes – Write Amplification.
Before geting into it, I'll reference the excellent graphic that Anand put in his SSD Relapse piece:
SSD controllers combine smaller writes into larger ones in an attempt to speed up the effective write speed. This falls flat once all flash blocks have been written to at least once. From that point forward, the SSD must play musical chairs with the data on each and every small write. In a bad case, a single 4KB write turns into a 2MB write. For that example, Write Amplification would be a factor of 500, meaning the flash memory is cycled at 500x the rate calculated in the paper. Sure that’s an extreme example, but the point is that without referencing amplification at all, it is assumed to be a factor of 1, which would only be the case if you were only writing 2MB blocks of data to the SSD. This is almost never the case, regardless of Operating System.
After posters on Slashdot called out the author on his assumptions of rated P/E cycles, he went back and added two links to justify his figures. The problem is that the first links to a 2005 data sheet for 90nm SLC flash. Samsung’s 90nm flash was 1Gb per die (128MB). The packages were available with up to 4 dies each, and scaling up to a typical 16-chip SSD, that only gives you an 8GB SSD. Not very practical. That’s not to say 100k is an inaccurate figure for SLC endurance. It’s just a really bad reference to use is all. Here's a better one from the Flash Memory Summit a couple of years back:
The second link was a 2008 PR blast from Micron, based on their proposed pushing of the 34nm process to its limits. “One Million Write Cycles” was nothing more than a tag line for an achievement accomplished in a lab under ideal conditions. That figure was never reached in anything you could actually buy in a SATA SSD. A better reference would be from that same presentation at the Summit:
This shows larger process nodes hitting even beyond 1 million cycles (given sufficient additional error bits used for error correction), but remember it has to be something that is available and in a usable capacity to be practical for real world use, and that’s just not the case for the flash in the above chart.
At the end of the day, manufacturers must balance cost, capacity, and longevity. This forces a push towards smaller processes (for more capacity per cost), with the limit being how much endurance they are willing to give up in the process. In the end they choose based on what the customer needs. Enterprise use leans towards SLC or eMLC, as they are willing to spend more for the gain in endurance. Typical PC users get standard MLC and now even TLC, which are *good enough* for that application. It's worth noting that most SSD failures are not due to burning out all of the available flash P/E cycles. The vast majority are due to infant mortality failures of the controller or even due to buggy firmware. I've never written enough to any single consumer SSD (in normal operation) to wear out all of the flash. The closest I've come to a flash-related failure was when I had an ioDrive fail during testing by excessive heat causing a solder pad to lift on one of the flash chips.
All of this said, I’d love to see a revisit to the author’s well-structured paper – only based on the corrected assumptions I’ve outlined above. *That* is the type of paper I would reference when attempting to make *accurate* arguments for SSD endurance.
Subject: Storage | July 2, 2012 - 09:21 PM | Tim Verry
Tagged: ssd, slc, server, sandisk, PCIe SSD, flash, enterprise, caching
Flash storage company Sandisk has recently jumped into the world of enterprise PCI-E caching SSDs – what they are calling Solid State Accelerators. Currently, they are offering a 200GB and 400GB model under the company’s Lightning PCIe series. The SSDs feature a proprietary Sandisk controller driving 24nm SLC NAND flash, a PCI-E 2.0 x4 interface, and maximum power draw of 15 watts.
The Lightning Accelerators use the NAND flash for Sandisk’s own foundry and offer a large performance boost for servers and workstations over hard drives and SATA SSDs. It is capable of 410 MB/s sequential reads or 110,000 IOPS. Further, when using 4KB and 8KB blocks, the drives can reach 23,000 and 17,000 read/write IOPS respectively. Other specifications include an average response time of 245 microseconds, and less than 30 millisecond maximum response times. The Solid State Accelerators also feature sustained read and write latencies as low as 50 microseconds.
Sandisk has built the drives so that they can be configured as boot drives, storage drives, or caching drives. The company supports up to 5 drives in a single system, for a maximum of 2TB of flash storage. In addition, Sandisk is offering up its Flashsoft software that allows the Lightning Accelerators to be used as caching drives on Windows-based systems. Unfortunately, that is an additional cost which is not included in the already pricey SSDs (good thing for corporate expense accounts!).
Speaking of pricing, the 200GB LP206M has an MSRP of $1,350 while the 400GB LP406M has an MSRP of $2,350. Both cards have five year warranties and a MTBF rating of 2 million hours. You can find more information on the Sandisk Website.
It will be interesting to see how this Sandisk accelerator stacks up to the likes of the Intel 910 and FusioIO drives! The FusionIO FX, for example, gives you 420GB of QDP MLC NAND for $2,495, which works out such that Sandisk has a slightly lower cost-per-gigabyte value and SLC flash. We will have to wait for some independant reviews to say which drive is actually faster, however.
Subject: Storage | May 3, 2012 - 05:10 PM | Jeremy Hellstrom
Tagged: TCS, Galatea Ultra-Rugged SSD, ssd, 100GB, slc, SandForce SF-1565
Just by their very nature SSDs are physically tough, with no moving parts like you find in platter based disks, so they are able to withstand much great acceleration forces ... or deceleration depending on how you look at it. TeleCommunication Systems is not a name you are likely to recognize when it comes to SSDs so you should take note of the Galatea Ultra Rugged SSD. The flash is just as tough, with 20,000 terabytes of write guaranteed along with 10 year data retention also guaranteed. Performance is also guaranteed thanks to the SandForce SF-1565 controller and Micron 25nm SLC flash. If there is an SSD likely to make it into orbit soon, this will probably be the one to do it. Check it out at SSD Review.
"This report covers the Telecommunications Systems (TCS) Galatea line of ultra-rugged SLC SSDs. Adhering to the MIL-STD-810 military specifications governing a multitude of ultra-ruggedized requirements, this SSD is designed for ultimate reliability in the harshest of environments. Designed and tested with the most hostile environments imaginable in mind, these SSDs are surely amongst the toughest storage mediums available."
Here are some more Storage reviews from around the web:
- Intel 910 400/800GB PCIe SSD Quick Preview - On The Bench and Pushing Out 1.9GB/s Performance @ The SSD Review
- Corsair Force Series 3 180GB @ Tweaktown
- Intel SSD 330 120GB / 180GB review @ Hardware.Info
- Intel 330 Series 120GB @ SSD Review
- ADATA Premier Pro SP900 (0-provision) 256GB @ Tweaktown
- Crucial Adrenaline 50GB m4 Cache SSD Review @ Legit Reviews
- Patriot Pyro SE 240GB SSD Review @ Hardware Canucks
- RunCore Pro V MAX 240GB @ Tweaktown
- Corsair Force GT 180GB SATA III SandForce SF-2282 SSD Review @ Hi Tech Legion
- MemoRight FTM Plus Slim 7mm 240GB @ Tweaktown
- Plextor M3P 256GB SATA 3 SSD @ SSD Review
- Crucial Adrenaline 50GB Solid State Cache Review @ circuitREMIX
- Kingston HyperX 3k 240GB SATA III SSD Upgrade Kit Review @ NikKTech
- Corsair Accelerator Series 60GB Cache SSD @ SSD Review
- Adaptec RAID 6805E RAID Controller @ TechwareLabs
- Western Digital VelociRaptor 1TB (WD1000DHTZ) Review @ TechwareLabs
- Synology DS212j, DS212, and RS212 review @ Hardware.Info
- 16 4- and 5-bay NAS devices roundup test @ Hardware.Info
- QNAP TurboNAS TS-259 Pro+ NAS Server Review @ NikKTech
- Hitachi 7K4000 / 5K4000 4 TB review @ Hardware.Info
- QNAP TS-879 Pro @ Legion Hardware
- Kingston Wi-Fi Drive @ Hardwarebistro
- Kingston USB-Flash Drive Roundup @ Rbmods
Subject: Storage | April 27, 2011 - 07:06 PM | Allyn Malventano
Tagged: tlc, ssd, slc, ocz, mlc, flash
A while back, Intel and Micron jointly announced the beginnings of 20nm flash memory production, promising a 50% increase in die count per wafer (or a 50% reduction in per die production cost, depending on how you slice it). This shrink only did just that - shrink the die. Capacity remained at 64Gbit (8GB).
A few days ago IMFT also announced another way to shrink that die, but this time keeping with the now 'old' 25nm process. It turns out they have refined 25nm to the point where consumer-grade TLC flash can be produced. TLC is Triple-Level-Cell. While SLC (Single) holds 1 bit per cell, and MLC (Multi) holds two, TLC holds 3 bits per cell. Compared to the MLC 25nm dies, this gives a capacity increase without changing much else. IMFT, however, is happy with the 8GB 'sweet spot', so instead of jumping to a 12GB die of the same physical size, they are opting to instead shrink the current 25nm die to 131mm^2.
25nm TLC die, same 8GB capacity, but less area than the 25nm MLC die.
This gives Intel and Micron two options for ultimately reducing the price of flash - either by shrinking the process and getting more 8GB MLC dies out of a 20nm wafer, or by squeezing more bits into each cell of existing 25nm flash.
This is good stuff. Let's hope it gets even more SSD's into even more machines this holiday season.
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