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
New vs Used SSD Performance
We begin our look at how the overhead of managing pages impacts SSD performance with iometer. The table below shows iometer random write performance; there are two rows for each drive, one for “new” performance after a secure erase and one for “used” performance after the drive has been well used.
| 4KB Random Write Speed | New | "Used" |
| Intel X25-E | 31.7 MB/s | |
| Intel X25-M | 39.3 MB/s | 23.1 MB/s |
| JMicron JMF602B MLC | 0.02 MB/s | 0.02 MB/s |
| JMicron JMF602Bx2 MLC | 0.03 MB/s | 0.03 MB/s |
| OCZ Summit | 12.8 MB/s | 0.77 MB/s |
| OCZ Vertex | 8.2 MB/s | 2.41 MB/s |
| Samsung SLC | 2.61 MB/s | 0.53 MB/s |
| Seagate Momentus 5400.6 | 0.81 MB/s | - |
| Western Digital Caviar SE16 | 1.26 MB/s | - |
| Western Digital VelociRaptor | 1.63 MB/s | - |
Note that the “used” performance should be the slowest you’ll ever see the drive get. In theory, all of the pages are filled with some sort of data at this point.
All of the drives, with the exception of the JMicron based SSDs went down in performance in the “used” state. And the only reason the JMicron drive didn’t get any slower was because it is already bottlenecked elsewhere; you can’t get much slower than 0.03MB/s in this test.
These are pretty serious performance drops; the OCZ Vertex runs at nearly 1/4 the speed after it’s been used and Intel’s X25-M can only crunch through about 60% the IOs per second that it did when brand new.
So are SSDs doomed? Is performance going to tank over time and make these things worthless?
"Used" SSD performance vs. conventional hard drives.
Pay close attention to the average write latency in the graph above. While Intel’s X25-M pulls an extremely fast sub-0.3ms write latency normally, it levels off at 0.51ms in its used mode. The OCZ Vertex manages a 1.43ms new and 4.86ms used. There’s additional overhead for every write but a well designed SSD will still manage extremely low write latencies. To put things in perspective, look at these drives at their worst compared to Western Digital’s VelociRaptor.The degraded performance X25-M still completes write requests in around 1/8 the time of the VelociRaptor. Transfer speeds are still 8x higher as well.
Note that not all SSDs see their performance drop gracefully. The two Samsung based drives perform more like hard drives here, but I'll explain that tradeoff much later in this article.
How does this all translate into real world performance? I ran PCMark Vantage on the new and used Intel drive to see how performance changed.
| PCMark Overall Score | New | "Used" | % Drop |
| Intel X25-M | 11902 | 11536 | 3% |
| OCZ Summit | 10972 | 9916 | 9.6% |
| OCZ Vertex | 11253 | 9836 | 14.4% |
| Samsung SLC | 10143 | 9118 | 10.1% |
| Seagate Momentus 5400.6 | 6817 | - | - |
| Western Digital VelociRaptor | 7500 | - | - |
The real world performance hit varies from 0 - 14% depending on the drive. While the drives are still faster than a regular hard drive, performance does drop in the real world by a noticeable amount. The trim command would keep the drive’s performance closer to its peak for longer, but it would not have prevented this from happening.
| PCMark Vantage HDD Test | New | "Used" | % Drop |
| Intel X25-M | 29879 | 23252 | 22% |
| JMicron JMF602Bx2 MLC | 11613 | 11283 | 3% |
| OCZ Summit | 25754 | 16624 | 36% |
| OCZ Vertex | 20753 | 17854 | 14% |
| Samsung SLC | 17406 | 12392 | 29% |
| Seagate Momentus 5400.6 | 3525 | - | |
| Western Digital VelociRaptor | 6313 | - |
HDD specific tests show much more severe drops, ranging from 20 - 40% depending on the drive. Despite the performance drop, these drives are still much faster than even the fastest hard drives.
Facebook
Twitter
RSS
250 Comments
View All Comments
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.