From: Josh Durgin <josh.durgin@inktank.com>
To: Travis Rhoden <trhoden@gmail.com>
Cc: ceph-devel@vger.kernel.org
Subject: Re: snapshot storage use
Date: Tue, 17 Jul 2012 11:17:56 -0700 [thread overview]
Message-ID: <5005AC54.6030708@inktank.com> (raw)
In-Reply-To: <CACkq2motpiYUmTNNJjFe-H0ZS95CaArz16MXMFxuqGHZ24Kt5A@mail.gmail.com>
On 07/17/2012 11:11 AM, Travis Rhoden wrote:
> Hey folks,
>
> Sorry if this info is covered elsewhere -- I searched but was unable
> to find a description of what I wanted.
>
> Roughly how much storage is used by snapshots? Is it really just
> marking the version of certain objects, such that multiple snapshots
> of the same (unchanged) object consume essentially no new space?
> Correspondingly, once that object is finally modified, it is copied
> and the snapshots still point to the original (old) copy? Is this
> done by using hardlinks or some other method?
Yes, snapshots are copy-on-write at the object level. On the osd, this
is either an efficient clone (btrfs) or a full copy of the object
(non-btrfs).
>
> Just wanted the 10,000 foot view explanation. =)
>
> Thanks,
>
> - Travis
prev parent reply other threads:[~2012-07-17 18:20 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-17 18:11 snapshot storage use Travis Rhoden
2012-07-17 18:17 ` Josh Durgin [this message]
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