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I created a Windows virtual machine in azure. By default it came with 2 drives.

  1. c:\ => with 30 GB
  2. d:\ => with 15 GB

I created a data disk of 10 GB and attached that to the virtual machine. I named the new drive as F:\

I installed required softwares like MySQL, HmailServer, etc to F:\ . I'm also hosting my websites from F:\

My question is, if a hardware failure occurs & the VM is restarted automatically by Azure on some other hardware what will happen? What will happen to the data on C:\ & F:\ ? ( I think d:\ will lose everything). Will the softwares like MySQL, HmailServer, etc & web sites continue to work as usual? Will that require any intervention from me?

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migrated from Dec 21 '12 at 0:12

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With Windows Azure Virtual Machines, first you will have default OS Disk which is used to create your Virtual machine and the data on this disk will be persisted. In this case your OS disk which is 30GB (If you created your VM from Gallery, then your OS disk will be 30GB default) and anything on this disk will be persisted.

Any Data disk you will to your Virtual machine will persist as well. So anything you will write on your Data Disk will persist as well.

During any H/W failure or any issue, both OS and Data Disk will persist and will be running as it was before. If you have stored your application either on OS disk and Data Disk, there will not be any problem with the application if your VM is reconfigured due to some issue.

Also if you delete your Virtual Machine, your OS and Data Disks are still persisted in your Azure storage so when you create another Virtual Machine using the previous OS disk, you can have exact same functionalities in your newly created Virtual Machine.

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Thanks for your clear & detailed reply. – R Arun Dec 20 '12 at 20:48

If there is any restart in the host, the azure should be telling you about this activity, usually via email.

  1. The only you should do is that just turn off the critical service such as mysql. You do not need to turn off the VM.

  2. Make your system High Available (redundant) and set it in the same Availability Set. This will prevent Azure to restart both of them at the same time so your system is still running when restart happend.


There is no email notif due to failure. In my experience with the unplanned VM restart (1 mail server with zimbra and 1 critical mysql db server), there are no damage to the data or the VM. All the softwares run well. But my suggestion is make the system HA so you have a backup if there is some issue due to failure.

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There's no email notification if a VM is restarted due to a failure. The only email notification is for host OS maintenance, which gives (I believe) a 6-hour window). Note that the question asked about impact to storage, not about how to properly shut down VMs (or services within a VM. – David Makogon Dec 23 '13 at 18:57
Thx. Updated the answer. In my experience with host maintenance, I got 8 hours window which give me one big headache. Now i implement HA and some monitoring tools. – Wicaksono Trihatmaja Dec 24 '13 at 3:19

I don't know why included "AWS" in question related to the Azure cloud.

But, when you talk about Windows Azure Virtual Machines, nothing is ever lost. A hardware failure may occur, your OS DISK (VHD) will be used to spin up a new VM, and your data disks (VHD) will be attached to the newly instantiated Virtual Machine. So you have full safety with WIndows Azure VM.

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It was a mistake, so I removed AWS from the question. Thanks for the reply. – R Arun Dec 20 '12 at 20:43

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