linux-kernel - Re: [patch] document flash/RAID dangers

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Message-ID: <20090829093804.GD1634@ucw.cz>
Date:	Sat, 29 Aug 2009 11:38:04 +0200
From:	Pavel Machek <pavel@....cz>
To:	Ric Wheeler <rwheeler@...hat.com>
Cc:	david@...g.hm, Theodore Tso <tytso@....edu>,
	Florian Weimer <fweimer@....de>,
	Goswin von Brederlow <goswin-v-b@....de>,
	Rob Landley <rob@...dley.net>,
	kernel list <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>, mtk.manpages@...il.com,
	rdunlap@...otime.net, linux-doc@...r.kernel.org,
	linux-ext4@...r.kernel.org, corbet@....net
Subject: Re: [patch] document flash/RAID dangers

>> Example I seen went like this:
>>
>> Drive in raid 5 failed; hot spare was available (no idea about
>> UPS). System apparently locked up trying to talk to the failed drive,
>> or maybe admin just was not patient enough, so he just powercycled the
>> array. He lost the array.
>>
>> So while most people will not agressively powercycle the RAID array,
>> drive failure still provokes little tested error paths, and getting
>> unclean shutdown is quite easy in such case.
>
> Then what we need to document is do not power cycle an array during a  
> rebuild, right?

Yep, that and the fact that you should fsck if you do.

> If it wasn't the admin that timed out and the box really was hung (no  
> drive activity lights, etc), you will need to power cycle/reboot but  
> then you should not have this active rebuild issuing writes either...

Ok, I guess you are right here.
									Pavel

-- 
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