[Openstack] Swift And Erasure Code Storage

Brent Troge brenttroge2016 at gmail.com
Wed Aug 13 22:06:22 UTC 2014

Thanks all for your quick responses and for the value you bring to the

I realized my terminology 'SNAFU' as soon as I hit send, so thanks for the

Lastly, can you provide an ETA as to when EC within Swift will become
production ready?
If that is confidential I understand.


On Wed, Aug 13, 2014 at 4:57 PM, Luse, Paul E <paul.e.luse at intel.com> wrote:

>  The answer totally depends on how you choose to configure EC.  We
> generally refer to the “extra storage” as the overhead of the durability
> policy.  For triple replication, obviously its 3x (you buy 3x the usable
> capacity you need).  For EC it depends not only on which scheme you choose
> but the partakers that you configure.  For example Swift will support a few
> different Read Solomon schemes out of the box (when its done) and from
> there you can choose the ratio of data:parity such as 10:4 where you’d have
> 14 total disks, 10 of them for data and 4 for parity.  In this scheme you
> could lose 4 disks and still recover your data and your overhead would be
> 1.4 (14/10) as opposed to triple replication of 3 (3/1)
> -Paul
> *From:* Brent Troge [mailto:brenttroge2016 at gmail.com]
> *Sent:* Wednesday, August 13, 2014 2:41 PM
> *To:* openstack at lists.openstack.org
> *Subject:* [Openstack] Swift And Erasure Code Storage
> With a 100% 'Erasure Code' policy how much extra storage is needed to
> satisfy a 1PB usable cluster ?
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