Azure VM - Temporary Storage drive - a thing of the past?

Question

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!

Answer 1

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.

Answer 2

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

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

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.

Answer 3

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