From: Duncan <1i5t5.duncan@cox.net>
To: linux-btrfs@vger.kernel.org
Subject: Re: SSD TRIM on balance
Date: Sat, 19 Apr 2014 04:59:40 +0000 (UTC) [thread overview]
Message-ID: <pan$d3f18$ce6243a7$353dc24b$c2a46503@cox.net> (raw)
In-Reply-To: 53515BB4.7070700@gmail.com
Sergey E. Kolesnikov posted on Fri, 18 Apr 2014 21:07:00 +0400 as
excerpted:
> I've recently rebalanced my btrfs (kernel 3.13) running on two SSD
> drives (raid-0) and a question arose.
> Does btrfs perform TRIM on SSD balance? Fs is mounted with 'ssd' option,
> but not 'discard'.
>
> It seems fstrim only trims free chunks in allocated space, so we
> possibly having a "trim leak" if no special treatment is taken on blocks
> reallocated during balance operation.
As a user and list-regular, I don't know the answer to your question as
I've not seen it come up before and don't recall seeing it covered on the
wiki or the like either, but you have a very good point... and question.
FWIW I'm on dual-physical-device-SSDs here too (tho on btrfs raid1 mainly
because I like having a second copy of everything to restore from in case
the one copy goes bad and fails checksum) and also don't use the discard
option. While I'm currently running nearly 50% overprovisioned and thus
the FTL has plenty of space to do its thing regardless of what I do with
trim on the actually partitioned space, you raise a very good question
indeed, one I wish I had thought to ask myself, and now that you have,
one I'd very much like an answer to as well.
=:^)
--
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
prev parent reply other threads:[~2014-04-19 4:59 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-18 17:07 SSD TRIM on balance Sergey E. Kolesnikov
2014-04-19 4:59 ` Duncan [this message]
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