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May be I'm missing something but at a glance new SSD-based m3.medium EC2 instance doesn't provide any disk performance advantage. I didn't run benchmark tools yet, but directory copying, directory deleting, and hdparm don't show any difference between system and SSD volumes - /dev/sda1 and /dev/sdb. Am I wrong? Or there is some special configs?

TIA, Vitaly

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2 Answers 2

the /dev/sda or /dev/xvda device continues on top of EBS volumes, SSD are only available as Ephemeral Storage.

When create your instance, select /dev/sdb as Instance Store 0 under storage session.

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fgbreel, thank you! I launched SSD instance via AWS portal, based on existing AMI image. I don't remember that I had an option to select "/dev/sdb as Instance Store 0", but i'll review it again. Is there a way to see type of storage into instance properties under AWS portal? –  Vitaly Feb 25 at 4:37
    
You're welcome! –  fgbreel Feb 25 at 4:38

You can run iostat to check the performance. First create a big file where /dev/xvdb or /dev/sdb is mounted on (write)

cd /mnt/sdb
dd if=/dev/zero of=filename bs=1 count=100000000 seek=1048575 

Then run (read):

cat filename

Then install iostat (Ubuntu):

sudo apt-get install sysstat

This is the output on an m3.medium after running the iostat command:

root@ip-10-113-150-143:/mnt# iostat
Linux 3.2.0-54-virtual (ip-10-113-150-143)  02/25/2014  _x86_64_    (1 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.77    0.03    4.24    0.29    3.56   91.11

Device:            tps    kB_read/s    kB_wrtn/s    kB_read    kB_wrtn
xvdap1            1.10        17.45        11.07     237589     150688
xvdb              0.28         0.14         8.45       1917     115108

root@ip-10-113-150-143:/mnt#

As you can see the performance on xvdb is slightly higher than in xvdap1 (sda) for writes (so you may be right) Where you really see the improvement is in reads. 17.45 kB_read/s.

Hope this helps.

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