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Date:      30 Mar 2001 15:36:18 -0500
From:      Randell Jesup <rjesup@wgate.com>
To:        Bakul Shah <bakul@bitblocks.com>
Cc:        Kirk McKusick <mckusick@mckusick.com>, arch@FreeBSD.ORG
Subject:   Re: Background Fsck
Message-ID:  <ybu8zlngfjx.fsf@jesup.eng.tvol.net.jesup.eng.tvol.net>
In-Reply-To: Bakul Shah's message of "Fri, 30 Mar 2001 09:53:06 -0800"
References:  <200103301753.MAA03709@valiant.cnchost.com>

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Bakul Shah <bakul@bitblocks.com> writes:
>But like Terry I worry about disks write errors or blocks
>going bad.  And not knowing how well the bg fsck (or for that
>matter soft-updates) copes with that gives me an uneasy
>feeling.  Perhaps bg fsck should not do anything if it
>discovers structural inconsistency?

        This worries me too.  However, "not doing anything" can be
a problem if the system isn't being actively monitored.

>I know I don't have to run it if I feel this way but the
>point is to understand the behavior.

        Yes.

>> Many improvements have been made to fsck over the years. Through
>> there are undoubtedly more that could be made, there are no big
>> easy improvements left.
>
>I was less than clear; what I was asking is if anyone has
>looked at whether the fsck *algorithm* is optimal.  I
>wondered about its complexity -- is it O(n^2) or O(n log n)
>or something else and whether it is the best possible
>algorithm.

        Also think about the memory usage requirements.  FS checkers on
big drives can be memory hogs; I don't know about fsck.  I'm guessing
that it's O(n) so long as you don't run over memory requirements, but
that could easily happen.

-- 
Randell Jesup, Worldgate Communications, ex-Scala, ex-Amiga OS team ('88-94)
rjesup@wgate.com


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