Subject: Storage, Shows and Expos | January 8, 2015 - 01:17 AM | Allyn Malventano
Tagged: CES, ces 2015, silicon motion, SM2256, ssd, tlc, slc
We first saw the Silicon Motion SM2256 controller at Flash Memory Summit, but now we've seen it live, in action, and driving several different types of TLC NAND.
Silicon Motion had this live demo running on a testbed at their suite:
The performance looked very good considering the 2256 is designed to efficiently push TLC flash, which is slower than MLC. As their representative was explaining that the SM2256 is currently being tested with Samsung, Toshiba, and SK Hynix TLC flash, I noticed the HDTune write trace:
Those familiar with HDTune and Samsung SSDs with Samsung's TurboWrite cache (from the 840/850 EVO) will recognize the above - the SSD begins writing at SLC speed and after that cache is full, the SSD then drops to writing at TLC speed. I specifically asked about this, as we've only Samsung flash provisioned with an SLC portion of each die, and the answer was that Toshiba and SK Hynix TLC flash also supports such a subdivision. This is good news, as it means increased competition from competing SSDs that can accomplish the same SLC burst writes as the Samsung EVO series.
We heard from a few vendors that will soon be launching SM2256 equipped SSDs this year, and we eagerly await the opportunity to see what they are capable of.
Follow all of our coverage of the show at http://pcper.com/ces!
Subject: Storage | October 6, 2014 - 02:51 PM | Jeremy Hellstrom
Tagged: ssd, slc, mlc, micron, M600, Dynamic Write Acceleration
The Tech Report took a different look at Micron's M600 SSD than Al did in his review. Their benchmarks were focused more on a performance comparison versus the rest of the market, with over two dozen SSDs listed in their charts. As you would expect the 1TB model outperformed the 256GB model but it was interesting to note that the 256GB MX100 outperformed the newer M600 in many tests. In the final tally the new caching technology helped the 256GB model perform quite well but it was the 1TB model, which supposedly lacks that technology proved to be one of the fastest they have tested.
"Micron's new M600 SSD has a dynamic write cache that can treat any block on the drive as high-speed SLC NAND. This unique feature is designed to help lower-capacity SSDs keep up with larger drives that have more NAND-level parallelism, and we've tested the 256GB and 1TB versions to see how well it works."
Here are some more Storage reviews from around the web:
- MyDigitalSSD BP4e mSATA SSD @ The SSD Review
- Top 10 SSDs: Price, performance and capacity @ The Register
- Micron M600 M.2 SATA SSD @ The SSD Review
- Some thoughts on the performance of SSD RAID 0 arrays @ Hardware Secrets
- Transcend SSD370 128GB SSD Review @ Legit Reviews
- Micron M600 SSD @ The SSD Review
- QNAP TS-653 Pro @ Legion Hardware
- QNAP SilentNAS HS-251 NAS Server Review @ NikKTech
- Mach Xtreme MX-ES Ultra SLC USB 3.0 Flash Drive @ The SSD Review
- Silicon Power Marvel M70 64GB USB 3.0 Flash Drive Review @ NikKTech
Introduction and Specifications
Today Micron lifted the review embargo on their new M600 SSD lineup. We covered their press launch a couple of weeks ago, but as a recap, the headline new feature is the new Dynamic Write Acceleration feature. As this is a new (and untested) feature that completely changes the way an SSD must be tested, we will be diving deep on this one later in this article. For the moment, let's dispose with the formalities.
Here are the samples we received for testing:
It's worth noting that since all M600 models use 16nm 128Gbit dies, packaging is expected to have a negligible impact on performance. This means the 256GB MSATA sample should perform equally to its 2.5" SATA counterpart. The same goes for comparisons against M.2 form factor units. More detail is present in the specs below:
Highlights from the above specs are the increased write speeds (no doubt thanks to Dynamic Write Acceleration) and improved endurance figures. For reference, the prior gen Micron models were rated at 72TB (mostly regardless of capacity), so seeing figures upwards of 400TB indicates Micron's confidence in their 16nm process.
Sorry to disappoint here, but the M600 is an OEM targeted drive, meaning its 'packaging' will likely be the computer it comes installed in. If you manage to find it through a reseller, it will likely come in OEM-style brown/white box packaging.
We have been evaluating these samples for just under a week and have logged *many* hours on them, so let's get to it!
Subject: Storage, Shows and Expos | September 16, 2014 - 02:29 PM | 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 - 06:08 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 18, 2013 - 01:12 AM | 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 - 04:05 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 - 04:15 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.