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Date:      Fri, 25 Dec 2009 12:23:31 +0100
From:      Solon Lutz <solon@pyro.de>
To:        Thomas Burgess <wonslung@gmail.com>
Cc:        freebsd-fs@freebsd.org
Subject:   Re: ZFS RaidZ2 with 24 drives?
Message-ID:  <982740779.20091225122331@pyro.de>
In-Reply-To: <deb820500912250311y14cd0975i4e3a28c5fea24789@mail.gmail.com>
References:  <568624531.20091215163420@pyro.de> <42952D86-6B4D-49A3-8E4F-7A1A53A954C2@spry.com> <957649379.20091216005253@pyro.de> <26F8D203-A923-47D3-9935-BE4BC6DA09B7@corp.spry.com> <1696529130.20091223212612@pyro.de> <op.u5gbvfgz8527sy@82-170-177-25.ip.telfort.nl> <deb820500912241646p7c8fd726n5c68895105e28907@mail.gmail.com> <1266543768.20091225120330@pyro.de> <deb820500912250311y14cd0975i4e3a28c5fea24789@mail.gmail.com>

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> Depending on tuning, you can make it flush to disk more often.  It is also highly dependent on how much memory you have.

At the moment: 4GB. I'm about to try upgrading it to 6GB.

Why can't it work like this all the time:

device     r/s   w/s    kr/s    kw/s wait svc_t  %b
da0        0.0 1907.4     0.0 65494.8    0   0.6   6
ad10     680.7   0.0 87132.0     0.0   35  43.7  92


Effectively, it transfers 8-10MB/s! Took 24h for 1.2TB...

> I know on my personal system, i see this happen a lot but it doesn't seem to have a hugely negative impact on
> performance for what i use my machine for.  Depending on your setup, you may want to try various sysctl settings.  I
> found that disabling prefetch can have a huge impact on some systems.

Prefect is not enabled because of RAM < 4GB...
Can you name an tuneable sysctls?


Best regards,

Solon




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