From: David Sterba <dsterba@suse.cz>
To: Paul Richards <paul.richards@gmail.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: Does balance implicitly defrag?
Date: Mon, 8 Jul 2013 23:12:08 +0200 [thread overview]
Message-ID: <20130708211208.GF18204@twin.jikos.cz> (raw)
In-Reply-To: <CAMoswei+L-kH_O9uRecOorpS6Kf5hnZ9j3nxZ36kzFR6G9uXeg@mail.gmail.com>
On Tue, Jul 02, 2013 at 02:28:25PM +0100, Paul Richards wrote:
> When I run "btrfs filesystem balance", does this implicitly
> defragment the filesystem? (Assuming there is plenty free space)
In some sense it defragments the filesystem. The blockgroups are moved
around based on the balance filter. Here a blockgroup consists of
various and unrelated file extents. Extents representing a single file
are not made contiguous, this is done by 'btrfs file defrag'.
I think that the final layout of the 1G-chunks is not necessarily
contiguous, ie. it depends on the chunk-allocator, the time of the
allocation request and there's nothing like "preallocate 30G for whole
balance and put all data together because the space is available".
david
next prev parent reply other threads:[~2013-07-08 21:12 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-02 13:28 Does balance implicitly defrag? Paul Richards
2013-07-08 21:12 ` David Sterba [this message]
2013-07-08 21:30 ` Paul Richards
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