According to this link: http://aws.amazon.com/ebs/details/#availabilityanddurability

It said:

Amazon EBS Snapshot can expect an annual failure rate (AFR) of between 0.1% – 0.5%, where failure refers to a complete loss of the volume. This compares with commodity hard disks that typically fail with an AFR of around 4%,

Assume AFR of a commodity disk a 4%, and if I use RAID 1, chance of losing a volume is 4% * 4% = 0.16%, so on average EBS is worst that a Raid 1 configuration of commodity hard disks right?

  • AWS, in general, takes the "you should be able to survive failures" approach. Netflix uses a tool called "Chaos Monkey" to cause intentional random outages of instances, availability zones, and even entire regions. techblog.netflix.com/2010/12/… – ceejayoz Apr 18 '14 at 19:47

Your math is off, but your conclusion is correct. The chance of losing a RAID1 volume is not the chance of any two commodity drives failing in a given year, it's the chance of two commodity drives failing at about the same time, which is much less likely.

Yes, EBS is less reliable than R1.


You are comparing a physical disk against a network connected volume which enables, among others:

  • Take and share snapshots, which also enables easily and fast cloning of data.
  • Dynamic size expansion
  • Up to 16TB of data per volume
  • Detach and attach volumes between servers with a couple mouse clicks or API calls
  • Usage monitoring trough integrated Cloudwatch metrics, which enables alarms and notification or even trigger code execution using Lambda functions.

Also, RAIDs of EBS volumes are perfectly viable on AWS by implementing it at the OS level, which means that the same benefit ratios can be achieved, only varying the base performance and durability of each storage technology.

The conclusion is that commodity storage hardware and EBS are simply not comparable just because both deliver a similar feature, which is block storage. The underlying technology and the use case they target is so different that the comparison you are trying to make soon derives in these kind of "nonsenses".

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