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Date:      Tue, 5 Aug 2014 21:19:41 -0400
From:      Paul Kraus <paul@kraus-haus.org>
To:        FreeBSD Questions !!!! <freebsd-questions@freebsd.org>
Subject:   ZFS under FreeBSD failure modes
Message-ID:  <BDD126F3-3DF2-4A96-A3CD-9C2C8CE220FE@kraus-haus.org>
In-Reply-To: <20140802213848.GC77128@neutralgood.org>
References:  <53DAFCF2.2070909@hiwaay.net> <alpine.BSF.2.11.1407312131550.50731@wonkity.com> <53DB9797.1010702@hiwaay.net> <20140801164335.GA16376@slackbox.erewhon.home> <53DBF71D.3080807@hiwaay.net> <20140801232843.GB17393@slackbox.erewhon.home> <53DCF32A.30700@hiwaay.net> <20140802185442.GA28910@slackbox.erewhon.home> <53DD533D.7090700@hiwaay.net> <alpine.BSF.2.11.1408021524130.36114@wonkity.com> <20140802213848.GC77128@neutralgood.org>

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On Aug 2, 2014, at 17:38, kpneal@pobox.com wrote:

> I'd be careful running ZFS on a machine that lacks ECC memory. Lots of
> people do it, but I'd be worried that ZFS would get itself into a =
state
> where you couldn't access anything.

I am startring to see comments like this on a more frequent basis. What =
is the failure mechanism you expect to run into here?

> UFS I believe handles some kinds of
> damage better than ZFS.

Can you please be specific. I reed asking this question in another =
thread and just received snide comments back. What *specific* failure =
modes, and I am looking for technical details here, does UFS handle =
better than ZFS and why? What is it about ZFS that does not handle that =
failure?

> When was the last time anyone heard of a UFS file
> system being so damaged that it couldn't be recovered?

Anecdotal evidence at best. I have plenty of anecdotal evidence that ZFS =
never looses data. I don=92t claim it as fact.=20

In the early years of ZFS (and in the early years of ZFS under FreeBSD) =
it was much more picky about how you did things. One example; an =
absolute rule of mine was to never, ever relocate drives from an =
IMPORTED zpool. I had seen too many reports of zpools being corrupted or =
otherwise rendered unable to be mounted when drives were moved around. =
Both the ZFS code and the underlying device driver code is much better =
today, so it is much less of an issue (but I still try to avoid it, I =
EXPORT the pool before I make any hardware changes).

--
Paul Kraus
paul@kraus-haus.org




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