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
SSD Aging: Read Speed is Largely Unaffected
Given the nature of the SSD performance-over-time “problem” you’d expect to only pay the performance penalty when writing files, not reading. And for once, I don’t have any weird exceptions to talk about - this is generally the case.
The table below shows sequential read performance for 2MB blocks on new vs. “used” SSDs. I even included data for a couple of the hard drives in the "Used" column; for those numbers I'm simply measuring transfer rates from the slowest parts of the platter:
| 2MB Sequential Read Speed | New | "Used" |
| Intel X25-E | 240.1 MB/s | |
| Intel X25-M | 264.1 MB/s | 230.2 MB/s |
| JMicron JMF602B MLC | 134.7 MB/s | 134.7 MB/s |
| JMicron JMF602Bx2 MLC | 164.1 MB/s | 164.1 MB/s |
| OCZ Summit | 248.6 MB/s | 208.6 MB/s |
| OCZ Vertex | 257.8 MB/s | 250.1 MB/s |
| Samsung SLC | 101.4 MB/s | |
| Seagate Momentus 5400.6 | 77.9 MB/s | - |
| Western Digital Caviar SE16 | 104.6 MB/s | 54.3 MB/s |
| Western Digital VelociRaptor | 118.0 MB/s | 79.2 MB/s |
The best SSDs still transfer data at over 2x the rate of the VelociRaptor.
Read latency is also extremely good on these worn SSDs:
I left the conventional hard drives out of the chart simply because they completely screw up the scale. The VelociRaptor has a latency of 7.2ms in this iometer test with a queue depth of 3 IOs; that's an order of magnitude slower than the slowest SSD here.
Since you only pay the overhead penalty when you go to write to a previously-written block, the performance degradation only really occurs when you’re writing - not when you’re reading.
Now your OS is always writing to your drive, and that’s why we see a performance impact even if you’re just launching applications and opening files and such, but the penalty is much less tangible when it comes to read performance.
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blackburried - Wednesday, March 25, 2009 - link
It's referred to as "discard" in the kernel functions.It works very well w/ SSD's that support TRIM, like fusion-io's drives.
Iger - Wednesday, March 25, 2009 - link
This is the best review I've read in a very long time.Thank you very much!
BailoutBenny - Tuesday, March 24, 2009 - link
Great in depth article on flash based SSDs. I'm waiting for PRAM though.orclordrh - Tuesday, March 24, 2009 - link
Very illuminating article, very well written and researched. It made me glad that I didn't pull the trigger on an SSD for my I7 machine and regret not buying OCZ memory! I'm interested in adding an SSD as the scratch disk for Photoshop CS4 to use. I don't really launch applications very often, say once a week on the weekly reboot and keep 6-8 apps open at all times. I have 12GB of memory for that. The benchmarks were very interesting, but what sort of activity does Photoshop scratch usage create? Large files or random writes? What type of SSD would be most cost effective here?An SSD does sound better than a SSD!
semo - Wednesday, March 25, 2009 - link
wait for ddr3 to enter the mainstream and buy loads of memory.use a ramdisk for your adobe scratch area. much faster than ssd and no wear to worry about (not that you would worry that much with modern ssds anyway).
http://www.ghacks.net/2007/12/14/use-a-ramdisk-to-...">http://www.ghacks.net/2007/12/14/use-a-ramdisk-to-...
there is also a paid for and more feature rich ramdisk out there. can't remember the name
strikeback03 - Wednesday, March 25, 2009 - link
I'll have to check when I get home, but I believe the recommended size for the scratch disk is upwards of 10GB. So would need a motherboard that supports a LOT of RAM to give enough to main memory plus a scratch disk.strikeback03 - Wednesday, March 25, 2009 - link
I was wondering the same thing. I'd guess it would be a lot of writing/erasing, so an SSD might not be the best from a longevity standpoint, but if your system is hitting the scratch disk often then the speed might make it worthwhile.mikepers - Tuesday, March 24, 2009 - link
Anand,I wanted to compliment you on what I think was an excellent article. This is the type of thing I really have always liked from Anandtech. The detailed background, the technical reasons for the issues and then a thorough review of the current state of things.
I just finished upgrading my desktop. The only remaining item I wanted to replace was the hard disk. I had been thinking about getting a Velociraptor but instead I just ordered a 60GB Vertex from Newegg.
Thanks again for all the work.
Mike P.
ameatypie - Monday, March 23, 2009 - link
That sure was a lot to take in! Fantastic article though, it has really opened my eyes to the possibilities that Solid State Drives provide. Probably wont be buying one in the immediate future given the so-called depression and such things, but i will certainly keep up with SSD progress.Thanks again for your fantastic articles - im sure im not the only one who really appreciates them :)
coopchennick - Monday, March 23, 2009 - link
Hey Anand, I just finished reading through this whole article and I'm very impressed with the thoroughness and how informative it was.You just acquired a new regular reader.