SSD versus Enterprise SAS and SATA disks
by Johan De Gelas on March 20, 2009 2:00 AM EST- Posted in
- IT Computing
Conclusion
The system administrators with high-end, ultra mission critical applications will still look down their nose at the Intel X25-E Extreme SLC drive: it is not dual ported (SATA interface) and it does not have a "super capacitor" to allow the controller to write its 16MB cache to the flash array in the event of a sudden power outage. For those people, the Enterprise Flash Drives (EFD) of EMC make sense with capacities up to 400GB but prices ten times as high as the Intel X25-E SLC drive.
For the rest of us, probably 90% of the market, the Intel X25-E is nothing short of amazing: it offers at least 3 to 13 times better OLTP performance at less than a tenth of the power consumption of the classical SAS drives. We frankly see no reason any more to buy SAS or FC drives for performance critical OLTP databases unless the database sizes are really huge. From the moment you are using lots of spindles and most of your hard disks are empty, Intel's SLC SSDs make a lot more sense.
However, be aware that these ultra fast storage devices cause bottlenecks higher in the storage hierarchy. The current storage processors seem to have to trouble scaling well from four to eight drives. We have witnessed negative scaling only in some extreme cases, 100% random writes in RAID 5 for example. It is unlikely that you will witness this kind of behavior in the real world. Still, the trend is clear: scaling will be poor if you attach 16 or more SLC SSDs on products like the Adaptec 51645, 51645, and especially the 52445. Those RAID controllers allow you to attach up to 24 drives, but the available storage processor is the same as our Adaptec 5805 (IOP348 at 1.2GHz). We think it is best to attach no more than eight SLC drives per IOP348, especially if you are planning to use the more processor intensive RAID levels like RAID 5 and 6. Intel and others had better come up with faster storage processors soon, because these fast SLC drives make the limits of the current generation of storage processors painfully clear.
Our testing also shows that choosing the "cheaper but more SATA spindles" strategy only makes sense for applications that perform mostly sequential accesses. Once random access comes into play, you need two to three times more SATA drives - and there are limits to how far you can improve performance by adding spindles. Finally, to get the best performance out of your transactional applications, RAID 10 is still king, especially with the Intel X25-E.
References
[1] Dave Fellinger, "Architecting Storage for Petascale Clusters". http://www.ccs.ornl.gov/workshops/FallCreek07/presentations/fellinger.pdf
[2] US Department of Energy. Average retail price of electricity to ultimate customers by end-use sector, by state. http://www.eia.doe.gov/cneaf/electricity/epm/table5_6_a.html
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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