Backup the data in cloud block storage

If you use a cloud provider's block storage, it warrants backup to avoid possible data loss in the event of an outage.

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A recent Amazon outage resulted in a small number of customers losing production data stored in their accounts. This, of course, led to typical anti-cloud comments that follows such events.

The reality is that these customers data loss had nothing to do with cloud and everything to do with a common misunderstanding about Infrastructure as a Service (IaaS) resources.

What happened?

Over Labor Day weekend there was a power outage in one of the availability zones in Amazon’s US-East-1 region.  Backup generators came on, but quickly failed for unknown reasons. (No explanation was ever provided why the generators failed so quickly.) Although Elastic Block Store (EBS) data is replicated between multiple servers, the outage affected multiple servers.  The bulk of data stored in EBS was fine or was able to be easily recovered after outage; however, .5% of the data was not able to be recovered. Customers among the .5% that did not have a backup of their EBS data actually lost data.

It is often said that you can outsource IT but you cannot outsource the responsibility for IT. If you are going to use another company's service to store your company's important data, you need to understand how that service works. That includes what native protection tools it offers and – even more importantly – what protection it does not offer. This article discusses the block storage offerings of major cloud providers, and a separate one will explain cloud-based object storage – services that operate (and are protected) very differently. The purpose, design, and protection capabilities of the two services couldn't be more different.

What is cloud block storage?

All major IaaS vendors provide block storage, which is essentially a very reliable virtual hard drive in the cloud. For example, Amazon has Elastic Block Store, Azure has Managed Disks, and Google has Zonal Persistent Disks. If you think of block storage in the cloud as nothing more than a very fancy hard drive, what you need to do to protect it will become immediately obvious. The challenge is that many people think that all cloud storage is automatically protected against everything, and that simply isn’t true.

Many cloud block volumes are protected via replication within an availability zone

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