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I'm hoping someone can help me understand some EBS Bottlenecks that we are experiencing with a new Windows SQL Server instance we're configuring. We're running some tests by conducting a full backup so we can see how the I/O performs. However, the backup causes I/O blocking issues.

Its an r3.4xlarge instance which should have 250MB/s throughput and we've set up EBS with 7500 IOPs

However, we're only ever achieving a maximum of the following according to Cloudwatch:

Read Bandwidth: 140,486 KiB/s
Write Bandwidth: 22,448 KiB/s
TOTAL: 162934 KiB/s or 166 MB/s

Read Ops: 3468 OPS/s
Write Ops: 592 OPS/s
TOTAL: 4060 OPS/s

We cant understand why we're never achieving maximum IOPs or maximum throughput. Where else could it be bottlenecking?

  • Is the ebs volume in the same zone of the ec2 windows instance? – Giova Jan 15 '16 at 8:42
  • If you run a backup to "nul:" (ie. just read the data) what throughput do you get? – Remus Rusanu Jan 15 '16 at 9:53
  • Thanks for comments. It seems we missed the 160MB/s throughput limit on each EBS volume. – Giles Hunt Jan 15 '16 at 12:02
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We have had this answer back from AWS Support which shows where the bottleneck is occurring:

If you would like to reach 250MB/s, the maximum throughput of r3.4xlarge, you can change the volume to Provisioned IOPS(io1). IO1 has maximum throughput of 320 MiB/s. Another approach is to build RAID 0 array with 2 gp2 EBS volume. You can see the guidance from link [2].

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