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Re: XFS hangs and freezes with LSI 9265-8i controller on high i/o

To: xfs@xxxxxxxxxxx
Subject: Re: XFS hangs and freezes with LSI 9265-8i controller on high i/o
From: Michael Monnerie <michael.monnerie@xxxxxxxxxxxxxxxxxxx>
Date: Thu, 14 Jun 2012 09:31:20 +0200
In-reply-to: <4FD8BBDF.8060503@xxxxxxxxxxxxxxxxx>
Organization: it-management http://it-management.at
References: <4FD66513.2000108@xxxxxxxxx> <6637532.ZKYiNbq2uo@saturn> <4FD8BBDF.8060503@xxxxxxxxxxxxxxxxx>
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Am Mittwoch, 13. Juni 2012, 11:12:15 schrieb Stan Hoeppner:
> This is the LSI/3ware firmware default policy Michael, so every user
> is safe out-of-the-box.  If the BBU/FBU is not present (never
> installed), or the control logic determines it is not functioning
> properly, the firmware disables writeback caching.
> In absence of paying attention to logs/alerts, one will know pretty
> quickly when the BBU has failed, as write performance with many/most
> workloads will fall off a cliff.

That's good, and I guess every serious raid with bbu behaves the same. I
just wanted to make a statement because many people read "maximum
performance" and want this then, without understanding the downsides aka
"all data can be gone if a crash destroys the right metadata".

I get calls from people then whining, and they expect me not yell at
them but be friendly, which I don't like ;-)

I prefer to not speak about max perf if it means "probably eats your
data". Maybe we should always write "set this for max performance" only
with secure values, and then extra "and set this for turbo boost, but it
eats your data on a crash". Hopefully this helps keeping people from
just reading "max perf" and forget about the "eats your data" part.

mit freundlichen Grüssen,
Michael Monnerie, Ing. BSc

it-management Internet Services: Protéger
http://proteger.at [gesprochen: Prot-e-schee]
Tel: +43 660 / 415 6531

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