ZFS performance help sought

Mason Loring Bliss mason at blisses.org
Thu Jan 21 23:28:19 UTC 2016

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

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 at blisses.org   ))   giants were standing on my shoulders. - Hal Abelson

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