Someone recently asked The SSD Guy if there is a way to determine whether an SSD is SLC, MLC, eMLC or TLC.
I found it a little odd to be asked this, since most vendors tell what kind of flash they use in an SSD’s specifications, especially if it’s SLC.
Not finding it there then the next thing I would look at is the price. Raw SLC NAND flash now sells for about 6-10 times as much as its MLC counterpart, so an SSD with a price of around $1/GB is likely to be MLC and one that sells for around $10/GB is probably SLC.
TLC SSDs are really rare. There is the 840 from Samsung and the Ultra II and X300 from SanDisk. It’s also pretty rare to find an SSD that is based on eMLC, because eMLC achieves its higher endurance by slowing the part down. There are other, better ways to extend endurance.
Now that you know all this, please note that the kind of flash used to produce the SSD is probably unimportant. Certain MLC SSDs outperform some SLC SSDs, both in speed and in endurance – it all has to do with the quality of the controller. Some useful comparisons of SLC and MLC SSD performance are in the post: “Not All SSDs are Created Equal“. There’s a thorough explanation of controller techniques in The SSD Guy’s series on SSD controllers.
Furthermore, NAND chips allow controllers to change flash pages inside the chip from TLC to MLC to SLC as needed, so some SSDs actually internally manage hot data to SLC and cooler data to MLC or TLC.
For those that have read this far, I would recommend changing your focus away from questions of SLC vs. MLC vs. TLC and focus instead upon the SSD’s published specifications (like speed and endurance) and on its SMART attributes. The SMART attributes will always tell you how your SSD is wearing, and the specifications will tell you how it is expected to perform.
If you don’t trust the manufacturer’s performance specifications, then I highly recommend using the SNIA performance test specification, which gives unbiased performance results for any SSD.
Samsung recently introduced its 3D V-NAND-based 850 SSD which, according to The Tech Report, uses the same MEX controller as the company’s 3-bit planar SSD, the 840, introduced last year.
Samsung said in its keynote speech at the 2013 Flash Memory Summit that V-NAND consumes an average of 27% less power and runs at least 20% faster than its planar counterpart in an SSD application, all while providing ten times the endurance. It’s only natural to assume that this would allow designers to produce a V-NAND SSD that would significantly outperform its planar NAND counterpart.
In a move that The SSD Guy wishes he had thought of for himself, SanDisk has begun to help corporations upgrade their fleets of notebook PCs by replacing their HDDs with SSDs.
SanDisk calls this program STAR for: “SanDisk Tech-Assisted Refresh”. According to the press release: “Through the STAR program, SanDisk relieves IT departments of having to manage all aspects of upgrading corporate laptops such as, endpoint inventory analysis, employee service scheduling, system upgrades, data migration, daily progress reporting, post-upgrade analysis and support.”
SanDisk points out that PCs slow down with disk utilization and software updates, lowering users’ productivity. Often faster storage can solve that problem.
This is not an altogether new Continue reading
Erik Logan of Pogo Linux sent me a link to an amusing & informative video he and his company put together called A Brief History of SSDs. In the video Erik (pictured) tells of Pogo Linux’ experience with SSDs.
The company has a lot of hands-on SSD experience: Pogo Linux ships servers and storage and has ramped SSD shipments (as a percent of all drives) from single digits three years ago to the point where SSDs now account for 31% of all drives they ship. Erik shared with me that: “Sorting through the Continue reading
Earlier this month Western Digital’s HGST division invited The SSD Guy to a launch of a number of products. On the HDD side there were:
- 6TB air HDD, HGST’s last air-filled enterprise HDD
- 8TB helium HDD, an incremental upgrade of last year’s 6TB helium HDD
- 10TB shingled helium HDD (pictured)
I view these as very solid evidence that HDD costs will continue to stay an order of magnitude cheaper than SSD costs, thwarting the price-per-gigabyte crossover that others have been predicting for years.
In fact, since my last post on the price crossover in 2011, very little has changed.
It’s safe to assume that the HDD industry will Continue reading
Someone recently asked The SSD Guy to guess what would be the largest amount of flash that could be fit into an SSD’s case. This sounded like a fun problem, so I did a “Back-of-the-Envelope” estimate to try and figure it out.
First of all, I would judge by this post’s picture that you could get no more than 20 chip packages (4 x 5) on one side of a PC board for a 2.5″ SSD. That’s probably an optimistic estimate.
If you ignore the controller that would allow you to squeeze 40 packages onto a single circuit board.
Certain high-capacity SSDs use a “Butterfly” design to fit three circuit boards into a single 2.5″ HDD housing. With three 40-package circuit boards you could fit 120 chip packages into the 2.5″ HDD housing.
Today’s densest flash chip stores 128 gigabits or 16 gigabytes. Samsung and SanDisk can stack 16 of these chips within a single package, making a 16 x 16 gigabyte or 256 gigabyte package. SanDisk just announced a 512 gigabyte SD Card that doubles Continue reading
Seagate announced last week that the company had shipped a total of 10 million Solid State Hybrid Drives (SSHDs) over the lifetime of the product. This is far short of expectations by The SSD Guy and a number of other analysts and industry participants.
Why were our expectations higher? There were a few reasons:
- The hybrid drive can be viewed as an evolution of the DRAM cache already incorporated into nearly all HDDs today. Replacing or augmenting an expensive DRAM cache with a slower, cheaper NAND cache makes a lot of sense.
- An SSHD performs significantly better than Continue reading
SanDisk has just introduced the Ultra II SSD, an upgrade of the company’s original Ultra drive. The new device is being promoted as a 28 times faster HDD replacement that offers faster boot-up, longer battery life, and shock resistance, in an approach that appears to be a throwback to the early days of SSDs where the point was to sell the technology rather than the product. Although the press release shows sequential read & write bandwidth numbers of 550 and 500MB/s, neither the press release nor the online product literature even mention IOPS or other measures that are now commonly used to compare one SSD against the other.
SanDisk does tout the fact that this SSD uses Continue reading
What is NVRAM? Quite simply, it’s DRAM or SRAM that has a back-up flash memory a small controller, and a battery or super-capacitor. During operation the DRAM or SRAM is used in a system the same way that any DRAM or SRAM would be used. When power is interrupted the controller moves all of the data from the DRAM or SRAM to the flash using the backup power from the battery or super-capacitor. When power is restored, the controller moves the contents of the flash back into the SRAM or DRAM and the processor can resume operation where it left off.
In some ways it’s storage and in some ways it’s memory, so Continue reading