SSD versus Enterprise SAS and SATA disks
by Johan De Gelas on March 20, 2009 2:00 AM EST- Posted in
- IT Computing
IOMeter/SQLIO Software Setup
Before we start with the "closer to the real world" OLTP tests, we decided to measure the disk component part of database performance with IOMeter and SQLIO. For these tests, we started with RAID 0 as we didn't want our RAID controller to be the bottleneck. Some benchmark scenarios showed that our hopes were in vain, as sometimes the RAID controller can still be the bottleneck as you will see shortly. We selected a 64KB stripe size as we assumed the intended use was for a database application that has to perform both sequential and random reads/writes.
As we test with SQLIO, Microsoft's I/O stress tool for MS SQL server 2005, it is important to know that if the SQL server database accesses the disks in random fashion this happens in blocks of 8KB. Sequential accesses (read-ahead) can use I/O sizes from 16KB up to 1024KB, so we used a stripe size of 64KB as a decent compromise. All tests are done with Disk Queue Length (DQL) at 2 per drive (16 for an eight drive array). DQL indicates the number of outstanding disk requests as well as requests currently being serviced for a particular disk. A DQL that averages 2 per drive or more means that the disk system is the bottleneck.
Next we aligned (more info here) our testing partition with a 64KB offset with the diskpart tool. There has been some discussion on the ideal alignment (512KB, one block?), but even Intel is not sure yet. So we chose the relatively safe 64KB boundary (which aligns with 4KB pages).
To keep the number of benchmarks reasonable, we use the following:
- RAID 0, RAID 10, or RAID 5; stripe size 64KB (always)
- Adaptive Read Ahead and Write-Back always configured on the RAID controller
- NTFS, 64KB cluster size
- Access block size 8KB (Random) and 64KB (Sequential)
This should give you a good idea of how we tested. The controllers available only support eight drives. As we wanted to test the "use more cheaper SATA disks" philosophy, we use two controllers combined with Microsoft's software RAID to test 16 drives. Software RAID is at least as fast as hardware RAID as we use the mighty 2.5GHz quad-core Xeon instead of the small dual-core Intel IOP 348 controller.
To make the graphs easier to read, we made all SATA disks measurements orange, all SAS disks measurements green, and all SATA-SSD benchmarks are blue.
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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