KfWiki: Seagate Momentus XT performance

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Seagate Momentus XT performance

Product: Seagate Momentus XT http://www.seagate.com/www/en-us/products/laptops/laptop-hdd/
It's not really an SSD, it's a "hybrid" drive from Seagate with 4G of SLC NAND cache. Let's see how it performs.

Background

I have a RAID1 array running with 2x WD SATA drives on a 3ware 9650SE without BBU. The WD's are WD6401AALS-00L3 and the Seagate is a ST95005620AS. All 3 drives are connected to the same controller. Both volumes are formatted with ext4. What I want is to have a drive with faster IO to store my vm images.

Bonnie benchmark

Western Digital: Test with 2G file

ism# bonnie++ -d /my/vm -r 512 -u root -s 2g -n0 -q -f -b
Version  1.96       ------Sequential Output------ --Sequential Input- --Random-
Concurrency   1     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
ism.comme.ca     2G           75460  10 81179  11           3460452  94 236.8   6
Latency                        1366ms    1345ms                56us     569ms

1.96,1.96,ism.comme.ca,1,1307255609,2G,,,,75460,10,81179,11,,,3460452,94,236.8,6,,,,,,,,,,,,,,,,,,,1366ms,1345ms,,56us,569ms,,,,,,

Seagate: Test with 2G file, which should fit in SSD cache:

ism# bonnie++ -d /my/vm2 -r 512 -u root -s 2g -n0 -q -f -b
Version  1.96       ------Sequential Output------ --Sequential Input- --Random-
Concurrency   1     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
ism.comme.ca     2G           97078  14 98015  16           3302575  89 316.2   8
Latency                        1067ms    1150ms               128us     322ms

1.96,1.96,ism.comme.ca,1,1307270620,2G,,,,97078,14,98015,16,,,3302575,89,316.2,8,,,,,,,,,,,,,,,,,,,1067ms,1150ms,,128us,322ms,,,,,,

Seagate: test with a 6G file, which does not fit in SSD cache

ism# bonnie++ -d /my/vm2 -r 1024 -u root -s 6g -n0 -q -f -b
Version  1.96       ------Sequential Output------ --Sequential Input- --Random-
Concurrency   1     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
ism.comme.ca     6G           99533  14 46875  15           128687  17 119.9   5
Latency                        1148ms     991ms               172ms     462ms

1.96,1.96,ism.comme.ca,1,1307271129,6G,,,,99533,14,46875,15,,,128687,17,119.9,5,,,,,,,,,,,,,,,,,,,1148ms,991ms,,172ms,462ms,,,,,,

There is a 28% increase with write speed. So how does it perform on application level?

VM Boot up time

I have a fresh installed RHEL6 64bit VM running on KVM. Boot up time is around 30seconds on the WD. When moved to the Seagate, the first boot also take 30 seconds. Probably because the data needs to be read from disk to cache. When I booted it the second time, it took only 21 seconds - a 30% decrease!

Conclusion

These tests may not be definitive. Some more researching into this drive reveals that the NAND cache are used only for read, and it's optimised for small files. The write performance over my WD raid may well be a indication of a slow RAID controller. Read performance is not shown with bonnie's benchmark, but it's certainly faster with rebooting the vm. But for HK$899, I'm pretty happy.

KfWiki : FileSystemsBenchMarkSDD

Seagate Momentus XT performance

Background

Bonnie benchmark

VM Boot up time

Conclusion