Windows Azure and Storage performance

For those that have been working with Azure for some time there are some challenges with delivering enough performance for a certion application or workload.
For those that are not aware Microsoft has put limits on max IOPS on disks which are attached to a virtual machine in Azure.  But note these are max limits and not a guarantee that you get 500 IOPS for each data disk.

Virtual Machine instance
Basic ( 300 IOPS) (8 KB)
Standard ( 500 IOPS / 60 MBPS) (8 KB)

There is also a cap for a storage account for 20,000 IOPS.

In order to go “past” the limit, Microosft has mentioned from time to time to use Storage Spaces (which is basically a software RAID solution which was introduced with Server 2012) in order to spread the IO load between different data disks. (Which is a supported solution)

http://blogs.msdn.com/b/dfurman/archive/2014/04/27/using-storage-spaces-on-an-azure-vm-cluster-for-sql-server-storage.aspx “physical disks use Azure Blob storage, which has certain performance limitations. However, creating a storage space on top of a striped set of such physical disks lets you work around these limitations to some extent.”

Therefore I decided to do a test using a A4 virtual machine with 14 added data disks and create a software pool with striped volume and see how it performed. NOTE that this setup was using regular storage spaces setup which by default uses a chuck size of 256 KB blocks and column size of 8 disks.http://social.technet.microsoft.com/wiki/contents/articles/11382.storage-spaces-frequently-asked-questions-faq.aspx#What_are_columns_and_how_does_Storage_Spaces_decide_how_many_to_use

I setup all disks in a single pool and created a simple striped volume to spread the IO workload across the disks (not recommended for redudancy!) and note that these tests were done using West Europe datacenter. And when I created the virtual disk I needed to define max amount of columns across disks.

Get-storagepool -FriendlyName test | New-VirtualDisk -FriendlyName «test» -ResiliencySettingName simple -UseMaximumSize -NumberOfColumns 14

Also I did not set any read/write cache on the data disks. Now I used HD tune pro since I delivers a nice GUI chart as well as IOPS.

For comparison this is my local machine with an SSD drive (READ) using Random Access testing.

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This is from the Storage space (simple virtual disk across 14 columns with 256 chucks) (READ)

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This is from the D: drive in Azure (note that this is not a D-instance with SSD)

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This is from the C: drive in Azure (which by default has caching enabled for read/write)

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Then when doing a regular benchmarking test with Writing a 500 MB file to the virtual volume on the disk.

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Then against the D drive

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Then for C:\ which has read/write cache activated I get some spikes because of the cache.

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This is for a regular data disk which IS not in a storage pool. (I just deleted the pool and used one of the disks there)

This a regular benchmark test.

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Random Access test

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Now in conclusion we can see that a storage space setup in Azure is by few precentage faster then a single data disk in terms of performance. The problem with using Storage Spaces in Azure is the access time / latency that these disks have and therefore they become a bottleneck when setting up a storage pool.

Now luckily, Microsoft is coming with a Premium storage account which has up to 5000 IOPS pr data disk which is more like regular SSD performance which should make Azure a more viable solution to deliver application that are more IO intensiv.