Re: CEPH Replication

[Gregory Farnum <gfarnum@xxxxxxxxxx>]

We went to 3 copies because 2 isn't safe enough for the default. With 3 copies and a properly configured system your data is approximately as safe as the data center it's in. With 2 copies the durability is a lot lower than that (two 9s versus four 9s or something). The actual safety numbers did not otherwise change materially for the firefly release, though.

-Greg

On Monday, December 7, 2015, Le Quang Long <longlq.openstack@xxxxxxxxx> wrote:

Hi all,

I have one question

Why did default replication change to 3 in Ceph Firefly? I think 2 copys of object is enough for backup. And increase the number of replication also increase latency when object has to be replicated to secondary and tertiory OSD.

So why default replication is 3, not 2 or 4 or other numbers?

Thanks and regards.

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