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We are just entering Azure world and will be migrating SQL server soon.I am trying to test throughput on Azure VM (DS13_V2) which is supposed to give 384MB/Sec as per documentation.

Here is the configuration :

a) No of cores : 8

b) Attached 2 disks (1TB each formatted with 64K block size) to the VM which are P30 disks(200mb/sec).

c) I have striped 2 disks into one and called it F: drive with total 2TB which in theory is capable of giving 400mb/sec.

Test: I ran SQLIO (with Test file size - 20GB on the striped drive F:) with multiple combinations and looks like throughput is throttled at 256mb/sec consistently. I even ran diskspd which also gives me the same 256mb/sec throughput.

Question: I am wondering where the bottleneck is or anything that i am missing as VM is capable of giving 384mb/sec and my striped disks are capable of giving 400mb/sec (200mb/sec each) wherein i should be seeing a throughput of 384mb/sec.

Please let me know if any suggestions would help me in doing a better storage test.

  • When you run this, what settings are you choosing for the test stride sizes? There is a limit on BOTH IOPs AND Throughput. The max IOPs on P30 is 5,000 per disk. – Sean says Remove Sara Chipps Jul 30 '16 at 23:57
  • Stride size is 64K – yvr238 Jul 31 '16 at 0:22
  • Did you use storage spaces to create the stripe? – Sean says Remove Sara Chipps Jul 31 '16 at 0:52
  • I created a resource group for the storage account and attached the 1TB disks and striped using Disk Management. – yvr238 Aug 1 '16 at 0:09
  • How many IOPs did the tests report? – Sean says Remove Sara Chipps Aug 3 '16 at 15:55
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Those numbers in your performance tests are accurate. Theoretical throughput does not match my experience, after migrating an environment to more than ten DS13v2 instances. I get between 220MB/s and 256MB/s, depending on the type of writes, even with P30s.

To answer your question, the bottleneck is the network itself, which links the drives to the VM.

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