From: Charles Forsyth <charles.forsyth@gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Subject: Re: [9fans] RAID box with plan9 filesystem
Date: Wed, 28 Dec 2011 13:16:52 +0000 [thread overview]
Message-ID: <CAOw7k5hKB85CQrM85-AyZ3vxsjdw+xhYRB2h+55tEuW8y09VYQ@mail.gmail.com> (raw)
In-Reply-To: <CAEAzY3830Df05HRfMYR-pySyGUYjCnVGq-05bamVzs1NaF0xJQ@mail.gmail.com>
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Many file servers using disk drives are "unreliable" if you shut them down
without saving data in memory first.
Both /sys/src/fs and disk/kfs force certain metadata updates to disk first
to try to ensure that the fs structure,
if not the content, remains consistent. In fact, disk/kfs does more than
the old file server (it forces indirect block
updates out as well). Disk/kfs only seemed less reliable than the old file
system because it is more likely
to be shut down without syncing. Also, the old file server could be
recovered from a consistent root
if the worm dump was used. If you sync, you shouldn't have too much trouble.
Of course, forcing write-through makes the file system slower than some
others
for updates. At the cost of some code complexity, fossil attempts to do
better, using a "soft update"
scheme to ensure or attempt to ensure that everything on disk is
consistent. It's mentioned
briefly in the paper.
On 25 December 2011 16:30, Aram Hăvărneanu <aram.h@mgk.ro> wrote:
> I
> have heard very good things about the reliability of both. You say
> kfs is not very reliable, oh well.
>
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prev parent reply other threads:[~2011-12-28 13:16 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-21 16:14 tlaronde
2011-12-24 13:42 ` Aram Hăvărneanu
2011-12-24 15:03 ` Steve Simon
2011-12-24 16:47 ` Anthony Sorace
2011-12-25 16:30 ` Aram Hăvărneanu
2011-12-26 11:34 ` Yaroslav
2011-12-27 14:34 ` Aram Hăvărneanu
2011-12-28 13:16 ` Charles Forsyth [this message]
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