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I learned that the VM resides in different disk drives so it's tolerant to faults.

Do I still need to backup my azure VM?

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Faults aren't the only concern. What if you accidentally delete important files and need to restore them? –  ceejayoz Apr 26 '13 at 0:14
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3 Answers 3

up vote 3 down vote accepted

Backup has at least two reasons:

  • Protection from hardware failure
  • Protection from software or human errors, or attackers

Do you trust MS to do all the right things to not loose your data under any circumstances? Are you sure you will never make an error deleting data you still need or be victim of a software error or an attack? If no, you need a backup.

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Yes.

RAID (disk redundancy, except in the case of RAID0) is not a backup. You still need to protect your files from accidential deletion, corruption, viruses/trojans and so on.

See the following helpful article: http://www.smallnetbuilder.com/nas/nas-features/31745-data-recovery-tales-raid-is-not-backup

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Funny that the article ends with "help from the cloud" –  Eduardo Molteni Apr 26 '13 at 9:50
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Good answers from others. Let me clarify what happens with your Virtual Machine in Azure.

Windows Azure has Blob, Table, and Queue storage. These are all considered durable storage in that every single blob (or table entity, or queue message) is triple-replicated within the datacenter, and beyond that, optionally geo-replicated to neighboring data center (on same continent). Blob writes are replicated instantly; that is, it's not eventual-consistency between spindles. The spindles would also be separated so that they're not all sitting on within the same physical location (that wouldn't be very durable if, say, a disk controller died and took out all 3 disks). Note: Geo-replication is not instant; it's an async operation to the neighboring data center. However: When the writes are performed in the neighboring data center, those writes are written to that data center's blob storage, which is also durable). You don't have access to the geo-replicated data; that's only accessible to Azure, in the event of a catastrophic event at the primary data center.

Your Virtual Machine VHD is stored in a blob, so it benefits from the durable nature of Azure blobs. Also: Any attached drive you create and add to your Virtual Machine is also backed by Blobs (and you may attach 2 x # of cores, up to 16 drives for 8-core box).

Durability aside, you still may want to back up your VM, for reasons already discussed in other answers. To do this, you may take advantage of async blob copy functionality (available in the Azure command line tools as azure vm disk upload). You can also create a blob snapshot, but that doesn't duplicate any data (unless you change individual blob pages, but that's a topic for another day). The blob-copy procedure is the way to go. And within the same data center, this is ridiculously fast. I'm able to copy a Linux VM image in just a few seconds (sometimes less). It will certainly be a slower operation between data centers, but that's to be expected (and I have done this several times).

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