The SSD Anthology: Understanding SSDs and New Drives from OCZ
by Anand Lal Shimpi on March 18, 2009 12:00 AM EST- Posted in
- Storage
OCZ Tries Again with the Vertex
This is Ryan Petersen:
He’s the CEO of OCZ Technology. He wasn’t too happy after my Intel X25-M SSD review.
Although that review was about the X25-M, it addressed a major shortcoming with a number of other SSDs in the market - the most popular at the time being OCZ’s Core line.
The problem with the Core line was that although they were competitively priced, they had a major performance issue: small file write latency. The problem manifested itself in system-wide stuttering during disk intensive multitasking. It wouldn’t take a lot to make those drives stutter, and until that article went live, everyone assumed that the problem was Windows, the disk controller, or something else.
I placed the blame on the drives and Ryan wasn’t all too happy.
We argued. A lot. He claimed it was unfair that I was comparing the Core series to Intel’s far more expensive X25-M; I argued that the user experience offered by his drives was inferior to that of a regular hard drive. We never really saw eye to eye on SSDs after that article.
Ryan told me the problem was a lack of cache, and that they’d have a future version of their SSD with a large off-chip DRAM cache. Ryan did not want to send me any more SSDs that didn’t have a cache on them. It wasn’t just OCZ, we had difficulty getting JMicron based SSDs from most manufacturers after that article. Manufacturers were pissed.
I offered to look at any new SSDs they had coming, regardless of who made the controller. But I made one thing very clear - I did not believe that the JMicron based drives were fit for sale. I felt that they were hurting the image of SSDs in the market and doing more harm than good. Ask any of the major players in the flash and OS industries and you’ll hear the same complaint. We need good SSDs in the market, not a mixture of great ones and bad ones.
In early December I got word from OCZ that their first drive with a DRAM cache was nearing final production. The controller was from a Korean company called Indilinx, with a number of ex-Samsung engineers. JMicron was out for this product, they didn’t have a suitable controller - the JMF602B was it. I won’t draw too much attention to the fact that if the JMF602B drives were indeed fine then there would be no need to consider another controller manufacturer.
The Indilinx Barefoot controller would support up to 64MB of off-chip DRAM, but have no on-die cache. All user data would be buffered in this memory. Now 64MB is more than enough to handle anything being written to the drive, but the memory is also used for the ARM7 based processor for its work in dealing with wear leveling and flash block cleaning (removing invalid pages).
There’s a key distinction here between the Barefoot and Intel’s controller - the X25-M doesn’t store any user data in its DRAM. Technically the Barefoot approach is no less prone to dataloss than a standard hard drive, but the Intel approach is a bit better. In the event of sudden power loss there’s a chance that some of the data in the Barefoot’s 64MB buffer could be lost before it’s committed to flash.
The OCZ Vertex drive would have a more heavy duty controller, with an ARM processor and a large off-chip DRAM to improve performance. To top it all off, OCZ would sell it at a price much lower than Intel’s X25-M. Could this finally be the affordable SSD we’ve been looking for?
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Jamor - Wednesday, March 18, 2009 - link
The best tech article I've ever read, and I've read a few.haze4peace - Wednesday, March 18, 2009 - link
Wow, excellent article and so much useful information in an easy to understand way. I have just recently been paying attention to SSDs and thanks to this article I am armed with the information to make the correct choice for my needs. Thanks AnandTech, its the deep and honest articles like these that keep me coming back for more.Alseki - Wednesday, March 18, 2009 - link
I just registered then simply to say, great article. Really informative and enjoyable to read.alexsch8 - Wednesday, March 18, 2009 - link
Anand,Thank you for this article, very informative.
Looking at the example you are giving with your self-manufactured SSD drive: If I save the DOC I use up a page. Based on what you are saying, if I make a change to that DOC, it would then be saved in the next page instead of overwriting the existing page? If that is true, then the File Allocation system (FAT or MFT) itself would contribute quite a bit to the 'filling up of pages' phenomena. Could you elaborate if the proposed file system for SSD addresses this?
Ytterbium - Wednesday, March 18, 2009 - link
Fantastic article, shame that the vendors blacklisted you for telling the truth and OCZ rock for working so hard to address issues.I'll be ordering my Intel SSD soon, I'll defintly consider the Summit when it comes out for my encoding rig as there sequental writes matter to me.
mindless1 - Wednesday, March 18, 2009 - link
Great even, but I've have to disagree with the significance of the passage that suggested the Indilinx controller makes data loss as bad on those SSD as on a conventional hard drive.The primary cause of data loss is mechanical or component failure, not power loss. If we want to consider power loss, it's not just the drive which is prone to lose data, the entire system memory suffers far more data loss than that.
Further, a sufficiently sized supercapacitor should keep the drive operating for a period of time beyond when the rest of the system would be operational, it could be sufficient for the controller to finish writing to flash all received data (or just use an UPS, that's what they're for?).
Second, I can't believe that OCZ only tests designs with HDTach and Atto, I think it more likely they knew of the problem but didn't expect anyone to find it so quickly, and felt the higher sequential speeds made it more marketable. This makes me feel that manufacturers, then online sellers should differentiate their drives with a standardized random read/write score.
What would be really nice is if the Indilinx based SSDs had an application available, similar to a HDD acoustic management bit changing app, that lets the owner set their own preference for IO versus sequential read performance.
gomakeit - Wednesday, March 18, 2009 - link
This is by far the BEST article on SSD I've ever read! Great job anand and yes I read every single word of it!MagicPants - Wednesday, March 18, 2009 - link
Don't they ever try using their own devices? One second of latency should slap any user in the face. It should be very easy for a manufacturer to build a system with their new technology put it in front of people and see what happens, but apparently they're not doing this.They wait for reviewers to do the work for them and then get upset when they find a problem.
What the manufacturers should be taking away from this article is:
1) Try your competitor's products
2) Try your own products
3) Try them in real life as opposed to synthetic tests
4) Compare everything you've tried and market the performance that matters
7Enigma - Thursday, March 19, 2009 - link
But that would make sense....and we know marketing rarely does.paulinus - Wednesday, March 18, 2009 - link
That art is great. Finally someone done ssd test's right, and said loud what we, customers, can get for that hefty pricetags.I've supposed that only choices are intel and new ocz's. Now I know, and big kudos for that.
Just need a bit more $$ for x25-m, it'll be ideal for heavy workstation use, and biggest vertex'll replace wd black in my aging 6910p :)