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Message-ID: <47D92BBB.6000203@emc.com>
Date: Thu, 13 Mar 2008 09:27:23 -0400
From: Ric Wheeler <ric@....com>
To: Lars Marowsky-Bree <lmb@...e.de>
CC: Daniel Phillips <phillips@...nq.net>,
Alan Cox <alan@...rguk.ukuu.org.uk>,
Grzegorz Kulewski <kangur@...com.net>,
linux-kernel@...r.kernel.org
Subject: Re: [ANNOUNCE] Ramback: faster than a speeding bullet
Lars Marowsky-Bree wrote:
> On 2008-03-11T03:50:18, Daniel Phillips <phillips@...nq.net> wrote:
>
>>> as well. In fact, the most common reason for unorderly shutdowns are
>>> kernel crashes, not power failures in my experience.
>> What are you doing to your kernel?
>
> I guess I'm being really vicious to them: I expose it to customers and
> the real world.
>
> My own servers also have uptimes of >400 days sometimes, and I wonder
> what customers do to the poor things.
>
> And yes, I'm not saying I don't see your point for specialised
> deployments (filesystems which are easy to rebuild from scratch), but
> transactional integrity is a requirement I'd rank really high on the
> desirable list of features if I was you.
>
>>> So "perfectly reliable if UPS power does not fail" seems a bit over the
>>> top.
>> It works for EMC :-)
>
> Where they control the hardware and run a rather specialized OS as well,
> not a general purpose system like Linux on "commodity" hardware ;-)
Actually, in Centera we use generic hardware with a fairly normal kernel
which has strategic backports from upstream (libata, nic drivers, etc).
No UPS in the picture. Data integrity is protected by working with the
application team to insure they understand when data is safely on the
disk platter and working with IO & FS people to try and make sure we
don't lie to them (too much ) about that promise.
The centera boxes are tested with power failure & error injection and by
all of our customers in all those ways customers do ;-)
ric
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