From: Roger Binns <rogerb@rogerbinns.com>
To: linux-btrfs@vger.kernel.org
Subject: Re: data DUP
Date: Sat, 20 Apr 2013 14:15:14 -0700 [thread overview]
Message-ID: <kkv0gv$jpo$1@ger.gmane.org> (raw)
In-Reply-To: <20130420204814.GN7639@carfax.org.uk>
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On 20/04/13 13:48, Hugo Mills wrote:> On Sat, Apr 20, 2013 at 01:17:06PM
- -0700, Roger Binns wrote:
>> Is there any particular reason why I can't use DUP for data?
>
> Technically, no. Performance is likely to suck if you use rotational
> disks, and you may find some SSDs deduplicate blocks, making it fairly
> pointless for those devices.
Wanting dup is because I care about resilience in the face of errors over
performance, so I don't actually care how bad performance sucks. I only
put data on SSDs that I can afford to lose (usually backed up to
Dropbox/github/spinning disks).
>> When I try to set it with balance there is a kernel message:
>>
>> btrfs: dup for data is not allowed
>
> What kernel and userspace versions are you using? I thought the
> restriction had been removed at some point (but possibly I'm just
> misremembering it).
Whatever Ubuntu 12.10 ships with. Kernel package is 3.5.0.27.43 and
btrfs-tools is 0.19+20120328-7ubuntu1. Note the message came from the
kernel so it would appear to be solely to blame for refusing my request.
> it can be quite hard to find every single implication of a feature when
> that feature gets changd/updated.
I'm more amused that someone went to the trouble of putting in kernel
detection and messages plus updating the documentation in order to prevent
using DUP for data!
Roger
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next prev parent reply other threads:[~2013-04-20 21:15 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-20 20:17 data DUP Roger Binns
2013-04-20 20:48 ` Hugo Mills
2013-04-20 21:15 ` Roger Binns [this message]
2013-04-20 21:23 ` Hugo Mills
2013-04-20 23:01 ` Roger Binns
2013-04-27 21:40 ` Calvin Walton
2013-04-27 23:29 ` Roger Binns
2013-04-28 2:53 ` Alex Elsayed
2013-04-28 8:29 ` Roger Binns
2013-04-22 13:37 ` David Sterba
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