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Date:      Thu, 21 Jan 2016 18:28:10 -0500
From:      Mason Loring Bliss <mason@blisses.org>
To:        dweimer <dweimer@dweimer.net>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: ZFS performance help sought
Message-ID:  <20160121232810.GJ4538@blisses.org>
In-Reply-To: <ea3f05f9a8c20bd62a1c391b432dafe2@dweimer.net>
References:  <20160121205139.GG4538@blisses.org> <ea3f05f9a8c20bd62a1c391b432dafe2@dweimer.net>

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On Thu, Jan 21, 2016 at 03:35:23PM -0600, dweimer wrote:

> Try Starting here:
> https://wiki.freebsd.org/ZFSTuningGuide#General_Tuning

I'd looked at that previously, but as noted, I'd already tried capping the
ARC, and txg.timeout is already five by default in FreeBSD. My reading about
prefetch_disable suggests that it's meant for big transactions like what I'm
doing, but I could be confused.

All that said, I wasn't setting write_limit_override, so I'm trying that, and
I'm cutting the txg.timeout back a couple seconds more.

Am I confused about prefetch, though? They're talking about it as being
problematic for small, random I/O operations, where I'm doing big, chunky I/O
operations.

Anyway, thanks for the ideas. I'll write back with results presently.

-- 
Mason Loring Bliss  ((   If I have not seen as far as others, it is because
 mason@blisses.org   ))   giants were standing on my shoulders. - Hal Abelson



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