SSD versus Enterprise SAS and SATA disks
by Johan De Gelas on March 20, 2009 2:00 AM EST- Posted in
- IT Computing
I/O Meter Performance
IOMeter is an open source (originally developed by Intel) tool that can measure I/O performance in almost any way you can imagine. You can test random or sequential accesses (or a combination of the two), read or write operations (or a combination of the two), in blocks from a few KB to several MB. Whatever the goal, IOMeter can generate a workload and measure how fast the I/O system performs.
First, we evaluate the best scenario a magnetic disk can dream of: purely sequential access to a 20GB file. We are forced to use a relatively small file as our SLC SSD drives are only 32GB. Again, that's the best scenario imaginable for our magnetic disks, as we use only the outer tracks that have the most sectors and thus the highest sustained transfer rates.
The Intel SLC SSD delivers more than it promised: we measure 266 MB/s instead of the promised 250 MB/s. Still, purely sequential loads do not make the expensive and small SSD disks attractive: it takes only two SAS disks or four SATA disks to match one SLC SSD. As the SAS disks are 10 times larger and the SATA drives 30 times, it is unlikely that we'll see a video streaming fileserver using SSDs any time soon.
Our Adaptec controller is clearly not taking full advantage of the SLC SSD's bandwidth: we only see a very small improvement going from four to eight disks. We assume that this is a SATA related issue, as eight SAS disks have no trouble reaching almost 1GB/s. This is the first sign of a RAID controller bottleneck. However, you can hardly blame Adaptec for not focusing on reaching the highest transfer rates with RAID 0: it is a very rare scenario in a business environment. Few people use a completely unsafe eight drive RAID 0 set and it is only now that there are disks capable of transferring 250 MB/s and more.
The 16 SATA disks reach the highest transfer rate with two of our Adaptec controllers. To investigate the impact of the RAID controller a bit further, we attached four of our SLC drives to one Adaptec controller and four on another one. First is a picture of the setup, and then the results.
The results are quite amazing: performance improves more than 60% with four SSDs on two controllers compared to eight X25-E SSDs on one controller. We end up with a RAID system that is capable of transferring 1.2GB/s.
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shady28 - Sunday, November 15, 2009 - link
I would have really like to see single drive performance of SAS 15K drives vs SSDs. The cost of a SAS controller ($60) + a 15K 150Gig drive ($110-$160) is less than any of the high end SSDs, and about the same as a low end SSD. It's a viable option to get a 15K Drive, but very difficult to see what is the best choice when looking at RAID configs and database IOPs.
newriter27 - Tuesday, May 5, 2009 - link
What was the Queue Depth setting used with IOmeter? Was it maintained consistently?Also, how come no response times?
mikeblas - Friday, April 17, 2009 - link
Intel has posted a firmware upgrade for their SSD drives which tries to address the write leveling problem. The patch improves matters, somewhat, but the overall performance level from the drives is still completely unacceptable for production applications.You can find it here: http://www.intel.com/support/ssdc/index_update.htm">http://www.intel.com/support/ssdc/index_update.htm
Lifted - Sunday, April 12, 2009 - link
I like it!turrican2097 - Monday, March 30, 2009 - link
Please mention or correct this on your article.1) You should mention that the price per GB is 65x higher than the 1TB drives, since you chose to include them.
2) Your WD is a poor performance 5400RPM Green Power drive: http://www.techreport.com/articles.x/16393/8">http://www.techreport.com/articles.x/16393/8
3) If you make such a strong point on how much faster SSDs are than platters, you can't pick the best SSD and then use the hardrives you happen to have laying around the lab. Pick Velociraptors or WD RE3 7200RPM and then Seagate 15K7.
Thank you
mutantmagnet - Monday, April 6, 2009 - link
It's irrelevant. Raptors don't outperform SAS which are better in terms of performance for the GB paid for. There's no need to belittle them when they are clearly aware of the type of point you are making and went beyond it.So far I've found these recent SSD articles to be a fun and worthwhile read; and the comments have been invaluable, even if some people sound a little too aggressive in making their points.
virtualgeek - Friday, March 27, 2009 - link
Just wanted to point this out - we are now shipping these 200GB and 400GB SLC-based STEC drives in EMC Symmetrix, CLARiiON and Celerra. These are the 2nd full generation of EFDs.Gang - this IS the future of performance-oriented storage (not implying it will be EMC-unique - it won't be - everyone will do it - from the high end to the low end) - only a matter of time (we're currently at the point where they are 1/3 the acquisition cost to hit a given IOPS workload - and they have dropped by a factor of 4x in ONE YEAR).
With Intel and Samsung entering to the market full force - the price/performance/capacity curve will continue to accelerate.
ms0815 - Friday, March 27, 2009 - link
Since modern Graphic cards crack passwords more than 10 times faster than a CPU, wouldn't they also be greate Raid Controllers with their massive paralel design?Casper42 - Thursday, March 26, 2009 - link
I would have liked to have seen 2 additional drives tossed into the mix on this one.1) The Intel X25-M - Because I think it would serve as a good middleground between the SAS Drives and the E model. Cheaper/GB but still gets you a much faster Random Read result and I'm sure a slightly faster Random Write as well.
2) 2.5" SAS Drives - Because mainstream servers like HP and Dell seem to be going more and more this direction. I don't know many Fortune 500s using Supermicro. 2.5" SAS goes up to 72GB for 15K and 300GB for 10K currently. Though I am hearing that 144GB 15K models are right around the corner.
Thanks for an interesting article!
MrSAballmer - Thursday, March 26, 2009 - link
SDS with ATA!http://www.youtube.com/watch?v=x4dxTRkODbE">http://www.youtube.com/watch?v=x4dxTRkODbE
http://fakesteveballmer.blogspot.com">http://fakesteveballmer.blogspot.com