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[Openstack] Fwd: Study of Swift performance degradation during drive failure


Hi All,

We are trying to understand and study how Swift handles drive failures.
>From the book we have learnt that a drive failure triggers replication by
default where as a node failure doesnt. We are trying to study the
performance impact of this replication on the handoff nodes.

If during the replication of an entire partition P to one of the handoff
nodes N1, an object is upload whose 1 of the 3 replicas is destined to node
N1, then is one operation going to have a higher priority ? i.e is does a
normal upload operation take priority over the replication that is in
progress or does it wait for the replication to complete.

Also in the above scenario I do not believe the user experiences much
performance degradation as the proxy server would have recieved the quorum
of successful responses from the other 2 nodes. This brings us to our next
question, what would be the simplest way to quantify the performance
degradation due to a drive failure(maybe multiple) on a Swift setup using
as few drives as possible.

Any help or pointers would be appreciated.

Thank you.
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