From: Ming Zhang <mingz@ele.uri.edu>
To: LVM general discussion and development <linux-lvm@redhat.com>
Subject: Re: [linux-lvm] 'snapshot' target still experimental :-(
Date: Wed, 01 Feb 2006 18:22:09 -0500 [thread overview]
Message-ID: <1138836130.4762.146.camel@localhost.localdomain> (raw)
In-Reply-To: <1138830708.15727.20.camel@pc.ilinx>
On Wed, 2006-02-01 at 16:51 -0500, Brian J. Murrell wrote:
> On Wed, 2006-02-01 at 13:29 -0800, Dan Stromberg wrote:
> > It just maintains a series of hardlink trees, so any time a file is
> > deleted or added, the actual disk usage increase is only due to the
> > changes.
>
> Yes, this is quite a popular technique. To be clear though, a change in
> a file does not consume just the amount of the change in the file on the
> backup target, but it consumes the entire size of the new file. A
> not-so-insignificant amount for very large files. This is where a
> (block level or filesystem level) snapshotting scheme would excel as it
> would likely only consume an amount of space rounded up to the next
> "unit" size more even for changes within a file.
it depends.
assume u have a huge text file. u change 1 char, the snapshot is useful.
u add one line at the beginning, the snapshot is useless here.
the offset shift.
some delta tech will be useful here.
>
> Indeed (and to keep quite on topic), perhaps rather than hardlink trees,
> LVM snapshots would be even more space efficient. Maybe that is what
> this thread has been about. I just jumped in. Apologies if it was.
>
> b.
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
next prev parent reply other threads:[~2006-02-01 23:22 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-01 16:37 [linux-lvm] 'snapshot' target still experimental :-( Kevin P. Fleming
2006-02-01 21:29 ` Dan Stromberg
2006-02-01 21:51 ` Brian J. Murrell
2006-02-01 22:26 ` Kevin P. Fleming
2006-02-01 23:22 ` Ming Zhang [this message]
-- strict thread matches above, loose matches on Subject: below --
2006-02-01 16:43 Steffen Plotner
2006-02-01 17:55 ` Kevin P. Fleming
2006-02-01 18:07 Steffen Plotner
2006-02-01 18:30 ` Alasdair G Kergon
2006-02-01 18:39 Steffen Plotner
2006-02-01 20:54 ` Ming Zhang
2006-02-02 3:02 Steffen Plotner
2006-02-02 13:17 ` Imre Gergely
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