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We are currently experiencing an issue where the IO performance of our SQL Server running on an Azure VM isn't quite up to snuff.

We are running a Azure VM (Standard DS2). This one has a 127 GB SSD C: drive throttled at 64 MB/s. We added an extra drive to this VM because we believe it should be able to perform faster than the limited 64 MB/s.

When doing copy operations (using AZCopy) to the newly added & faster F: drive we can see that the IO speeds are a lot higher. However, when restoring a database backup from this new & fast F: drive to a location on that same drive we're still getting throttled at 64MB/s.

We've contacted Microsoft about this but up until now they were unable to provide a proper explanation. Anyone has any experience with this?

Attached you'll find a screenshot of the performance monitor during the restore, showing that the read & write operations are only happening on the new F: drive, while showing a fairly stable 64MB/s.

Performance monitor during restore of database

  • The new drive that was added, was that from the same storage account ? – karun_r Oct 21 '16 at 14:06
  • The new drive is a Premium (SSD). Normally this one should get around 200 MB/s throughput. – Jens Oct 21 '16 at 14:10
  • How many disks does that drive have ? – karun_r Oct 21 '16 at 14:18
  • @karun10 As far as I know, just this one F drive. – Jens Oct 21 '16 at 14:19
  • Ok and when you face these throttling, is your VM getting rebooted ? – karun_r Oct 21 '16 at 14:57

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