From: Duncan <1i5t5.duncan@cox.net>
To: linux-btrfs@vger.kernel.org
Subject: Re: Putting very big and small files in one subvolume?
Date: Tue, 19 Aug 2014 04:07:06 +0000 (UTC) [thread overview]
Message-ID: <pan$644f0$9bc28c9e$b8087cfe$5c092f90@cox.net> (raw)
In-Reply-To: lstftk$tmt$1@ger.gmane.org
Martin posted on Mon, 18 Aug 2014 19:16:20 +0100 as excerpted:
> Also, for the file segment being defragged, abandon any links to other
> snapshots to in effect deliberately replicate the data where appropriate
> so that data segment is fully defragged.
FWIW, this is the current state.
The initial attempt at snapshot-aware-defrag was committed to mainline
(the kernel release is listed in the wiki's changelog page) but people
quickly ran into scaling issues with multi-thousand-snapshot systems as
well as quotas that weren't originally expected or, I guess, tested, pre-
mainline-merge, so they ended up reverting the snapshot awareness
temporarily, until they could come up with something more scalable. I
believe they've addressed some of that now, but I'm not sure it's yet
scaling the way the original trial suggested it needed to, and snapshot-
aware-defrag remains disabled for the time being.
So at least currently, defragging isn't snapshot aware, and as a result,
if the filesystem is highly fragmented, attempting to defrag will
increase space usage substantially as all those snapshot links are broken
in ordered to defrag the file on the currently mounted and being defragged
snapshot.
--
Duncan - List replies preferred. No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master." Richard Stallman
next prev parent reply other threads:[~2014-08-19 4:07 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-17 8:56 Putting very big and small files in one subvolume? Shriramana Sharma
2014-08-17 12:31 ` Duncan
2014-08-17 14:51 ` Russell Coker
2014-08-18 18:16 ` Martin
2014-08-19 4:07 ` Duncan [this message]
2014-08-19 5:26 ` Duncan
2014-08-29 16:04 ` Shriramana Sharma
2014-08-29 16:24 ` Hugo Mills
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