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Date:      Thu, 08 Aug 2013 22:04:07 +0100
From:      Frank Leonhardt <frank2@fjl.co.uk>
To:        freebsd-questions@freebsd.org
Subject:   Re: Terrible disk performance with LSI / FreeBSD 9.2-RC1
Message-ID:  <520407C7.9080603@fjl.co.uk>
In-Reply-To: <02C07E9F-ABB3-4A38-9638-21F913A08EC1@elde.net>
References:  <CABXB=RSRnB41yjq5Qcbiz-JCRssNwx2AatJ2Dn+HhuD9GaBh+w@mail.gmail.com> <CAEhBLvg7ZUMja5zpFm2UQBXESW-0fL9L7EatR2aasstXd8ALHA@mail.gmail.com> <CABXB=RRvp0BLURq7M9iBb5anqaGsrvXeA1WmAroNji6bZP8p4w@mail.gmail.com> <5202C558.3010305@fjl.co.uk> <02C07E9F-ABB3-4A38-9638-21F913A08EC1@elde.net>

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On 08/08/2013 12:42, Terje Elde wrote:
> On 8. aug. 2013, at 00:08, Frank Leonhardt <frank2@fjl.co.uk> wrote:
>> As a suggestion, what happens if you read from the drives directly? Boot in single user and try reading a Gb or two using /bin/dd. It might eliminate or confirm a problem with ZFS.
> If not too inconvenient, it'd be very interesting to see what'd happen if you were to physically disconnect (data and power) 5 of the 6 drives, then boot and dd from the remaining disk to /dev/null. Then repeat with another drive.
>
> You could boot from USB to leave the system itself otherwise untouched.
>
> The reason I'm suggesting is that I'm wondering if this can be down to a power or cable-issue, locking things up or causing retransmits, etc.
>
> Not sure if this would always be logged, others might be able to enlighten that issue.
>
> Terje
>
>
And while you're at it, could you post the output of diskinfo -v 
/dev/[slices] - check the cylinder alignment and so on if you haven't 
already.

Regards, Frank.




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