
Ask HN: Does AWS EBS have contradictory availability and durability guarantees? - ozgune
I&#x27;m going over AWS EBS product pages.<p>* EBS provides an availability guarantee of 99.999% (https:&#x2F;&#x2F;aws.amazon.com&#x2F;ebs).<p>* EBS provides a durability guarantee of 99.8-99.9% (https:&#x2F;&#x2F;aws.amazon.com&#x2F;ebs&#x2F;details&#x2F;#AvailabilityandDurability).<p>I don&#x27;t follow how these two numbers add up however. If you&#x27;re losing data %0.1-0.2 of the time, how can you provide availability guarantees that are 99.999%?<p>Is this because one of the guarantees is dated? Or does AWS consider available as &quot;hey, we lost your data but you can still access EBS&quot;? (doubt it)<p>I&#x27;m asking because I was reading this post (goo.gl&#x2F;eNhxaj) on HA and Disaster Recovery in Citus Cloud. I thought the author made a mistake in the second or third paragraph, but found that the links actually said the same things.
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misframer
Could it be that they're only providing 99.999% availability for volumes that
haven't failed?

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davismwfl
They are two different terms.

Availability, the chance when you ask for the data it won't be there, 99.999%
chance it will be.

Durability, the chance you will loose data and it will never be available is
rated at 99.8% chance you won't.

Unless I misunderstand something.

