Benchmark: Rackspace’s block storage SATA vs. SSD vs. VM disk

Rackspace offers 2 types of block storage:

Standard (SATA) @ $015/GBandHigh-Performance (SSD) @ $0.70/GB

Seeing that the SSD storage is 4x the cost of SATA I decided to see if the performance is also 4x.

Lets see.

The setup:

An 8GB(RAM) system running ubuntu 12.04&2 100GB volumes with the xfs file system mounted with the following options:

/dev/xvdb   /fast     xfs noatime,nodiratime,allocsize=512m   0   0  /dev/xvdd   /slow     xfs noatime,nodiratime,allocsize=512m   0   0

Basic test using dd:

I’ve benchmarked lots of storage systems in the past and I always like to start out with dd.I do this because it doesn’t take anytime to set up and should give you some idea of how it performs.

In this test I create a 20GB file on each mounted filesystem using the following command:

dd if=/dev/zero of=10GB.file bs=1M count=20k

The results are a little surprising:

Volume write performance:

standard            105 MB/shigh-performance        103 MB/sthe hosts's own volume      135 MB/s

Wow, not what are were hoping for.I ran this test several times and the “high-performance” storage was always the slowest.To quote Homer Simpson “Doh!!”


I ran bonnie with the following args, basically I specified double the amount of RAM for the test.

bonnie++ -s 16g

For sequential reads and writes they were about the same, this is expected as dd already showed this:

Volume                sequential reads            sequential writes  standard              95981/sec                   16564/sec  high-performance      95927/sec                   15633/sec  localVM               108463/sec                  1208/sec

The results now show where the high-performance excels which is random seeks.

Volume                random seeks  standard              473.4/sec  high-performance      1969/sec  localVM               578.6/sec


The question was:Does the 4x cost of high-performance storage perform 4x?

The answer is yes.

Nice job rackspace.

However, as with the sequential numbers from above it doesn’t always out perform standard or local disk. So before you decide to use the more expensive option benchmark your application on it.


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