From owner-freebsd-fs@FreeBSD.ORG  Wed Apr  4 01:50:39 2012
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Date: Tue, 3 Apr 2012 20:50:33 -0500 (CDT)
From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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To: Julian Elischer <julian@freebsd.org>
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Cc: FreeBSD Current <current@freebsd.org>, fs@freebsd.org
Subject: Re: "trim/discard" success story
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On Tue, 3 Apr 2012, Julian Elischer wrote:
>
> for flash drives this is great news..
> Now if ZFS would get trim support, that too would be great.

The major unknown issue with trim is how well the drives 
schedules/defers the trim operation so that it does not interfer with 
other I/Os.  Also, it would be really bad if the drive applied trim 
after the block had been re-allocated for a write.  It would also be 
really bad if the drive loses unrelated data if there is a power fail 
during trim.

If writes get blocked by a pending trim, then trim would not help 
very much.

Bob
-- 
Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/