1

On m3.xlarge instance (EBS Optimized – True) :

There are two EBS disks: /mnt/data0, /mnt/data1

Single dd:

dd bs=1M count=1024 if=/dev/zero of=/mnt/data0/test conv=fdatasync

1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB) copied, 15.9016 s, 67.5 MB/s

Two parallel dd's:

1073741824 bytes (1.1 GB) copied, 29.2529 s, 36.7 MB/s

1073741824 bytes (1.1 GB) copied, 33.8585 s, 31.7 MB/s

Clearly, overall EBS throughput is bottleneck. Is it expected?

If total EBS throughput is limited regardless of number of volumes, what is the point in EBS striping?

2

Looks like there is single network link between instance and EBS cloud. The throughput is described here: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/EBSOptimized.html

So the answer is, unless IOPS limit is hit, adding more EBS disks won't improve overall EBS performance of the instance.

0

For me, the main benefit of having multiple smaller EBS volumes rather than one massive one is cost management.

As an example right now on our DEV server, we have 3 x 100 GB EBS volumes attached with ZFS (configured in raidz1 but that's because I'm paranoid about data loss).

The devs keep telling me that we will need upwards of 1 TB worth of space, but until we need it I don't have to provision it. This keeps our costs as low as possible.

  • I would say single 300Gb EBS would be faster, not to mention bigger, than your current setup. Alas, paranoid does not come free. – Ivan Balashov Aug 11 '14 at 16:32

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