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I am confused about the Azure VM setup. I am trying to setup a SQL Server and the guidelines suggest that if your DBs are larger than 10GB, that you should setup a seperate Data Disk in Azure Storage. But all the documentation explicitly says not to use the D: Temporary Storage as it is volatile across reboots.

I completely understand this. The issue I have is that when I create a new VM, (I just created a SQL 2012 Web on 2008 R2 SP1 from the gallery), I get a single C: drive of about 128GB. When I then attach an empty data disk through the portal, it appears as D: and is called Temporary Storage.

My understanding is that this drive is not temporary storage (volatile) as I have created it through the portal as a data disk.

Is this a hangover from a past Azure configuration? I gather the VMs used to come with a 30GB OS drive but now come with a 128GB OS drive. Is this something to do with it?

I'm pretty confused!

gregpakes
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3 Answers3

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The way it works, the D drive is the 70GB temp (volatile) drive (at least with Windows Server 2012):

enter image description here

Here, I just attached an empty disk and refreshed the windows Server disk manager. I then go to format it:

enter image description here

Once formatted, my new 20GB disk is assigned to F (and I still have a 70GB temp drive). This drive, backed by blob storage, is durable.

enter image description here

David Makogon
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  • Hi David. My OS is 2008R2 and when it only came with a C drive. There was no D drive. I then attached an Empty Disk (through the portal) and a D drive appeared and it was named "Temporary Storage". That is the source of my confusion. – gregpakes Jun 12 '13 at 06:59
  • Interesting. How did you set up your VM? I was intrigued, so I just spun up a brand new Windows 2008R2 SP1 Virtual Machine from the gallery. After initial bootup, I RDP'd in and opened Disk Management. I had both a C: drive and a 70GB D: drive labeled `Temporary Storage`. – David Makogon Jun 12 '13 at 14:22
  • Thanks for doing that. Something is very fishy. I just provisioned a new version of the same VM again from the gallery and it does indeed have a D: labeled `Temporary Storage`. So I RDP'd back into the original one and looked in `Disk Management`. I have the following: Disk 0 C: 127GB NTFS, Disk 1 D: 135GB NTFS, Disk 2 128GB Unallocated. How can I tell which disk is the volatile one? – gregpakes Jun 12 '13 at 14:42
  • 135GB correlates with a Medium instance's temporary storage size (see [this page](http://msdn.microsoft.com/en-us/library/windowsazure/dn197896.aspx) for details around VM sizes and related storage. – David Makogon Jun 12 '13 at 14:58
  • Thanks Dave. I think i just got myself a bit confused to be honest. Certainly the Temporary Storage drive was not initialized on first boot. Also it does not seem volatile across reboots. I have shut down the VM and the files remain. – gregpakes Jun 12 '13 at 15:06
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When you are using Azure VMs - the OS drive & the Data drives are backed by Azure Blob Storage (the VHDs are Page Blobs). The OS disk size limit during most of the CTP was 10GB, but was raised around the time the feature shipped to the larger 128GB. The deciding factor for Data Drive/No Data Drive/Lots of Data Drives (Max = 16) for SQL is more a function of your IOPS requirements than either the size of the DB corpus or the relative drive size.

For SQL workloads in a VM, I would strongly recommend reviewing:

http://go.microsoft.com/fwlink/?LinkId=306266

This is a performance paper based on the latest Azure bits, developed by the SQL team (updated June 2013).

Pat

Pat Filoteo
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  • Thanks for the document I will give it a good read. Sadly though the "Disk types and configurations" section just adds to the confusion of my original question. It says "Temporary local disk (non-persistent): Each virtual machine that you create has a temporary local disk, the D: drive and which is labeled as TEMPORARY STORAGE." The issue is that my VM did not come with a D:, it only came with a C:. When I added a new empty disk from the portal, it appeared on my VM as D: and it was labeled as temporary storage. So now i'm really confused. – gregpakes Jun 12 '13 at 07:03
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In the interest of providing an answer to this question.

I think it was just an anomoly. @DavidMakogon helped me go through what was expected and it seems that my first VM simply didn't initialize the Temporary Drive on first boot, so this caused lots of confusion.

It's all working as expected now.

gregpakes
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