I'm creating a new Storage Pool and Virtual Disk on a Windows Server 2012 R2 machine on Azure. Can I just pick the Simple layout which doesn't account for a single disk failure because none of my disks will ever fail? The disks are backed by Azure's Storage system so shouldn't they never fail since they aren't real disks in the first place?

What are some of the advantages/disadvantages of choosing a more fault tolerant layout?

  • Never underestimate the power of Murphy's law. > If anything can go wrong, it will > If anything just cannot go wrong, it will anyway So if you cannot afford the failure, plan for it. – Fox Mar 16 '15 at 15:55
  • But if there's a catastrophic outage of Azure storage, it won't matter if I'm using Mirror, Parity or Simple layouts will it? – wwarren Mar 17 '15 at 0:42

All data in Azure Storage is, at a minimum, triply replicated locally in a fully-consistent mode. This means that the data in a VHD backed by Azure Storage, which the OS Disk and Data Disks are, is stored on 3 independent compute nodes. You likely won't gain much by duplicating that effort - so should not need to mirror VHDs.

  • OK, so the Simple layout should be good if the VHDs are backed by Azure Storage then. There's no need to use Mirror or Parity – wwarren Mar 17 '15 at 0:38
  • Correct. If you are going to use software raid just go for performance, that is, split the data among several disks without worrying about data loss. – Bruno Faria Mar 17 '15 at 13:13

There is no need indeed for using a mirror or a parity to protect the disks, however, this doesn't mean that your data inside the disks is protected, you would still need to take backup for the data inside the disks.

Imagine that you have a file stored on Azure storage, depending on the setup you might have 3 or 6 replicas of that file, if you by mistake overwrite something on the file or simply delete the file all together, your mistake will be replicated 3 or 6 times, the actual disks are not harmed, but your data on the disks is.

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