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Re: Which FileSystem do you use on your postfix server?

To: Wietse Venema <wietse@xxxxxxxxxxxxx>
Subject: Re: Which FileSystem do you use on your postfix server?
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Mon, 3 Nov 2008 08:44:45 +1100
Cc: Eric Sandeen <sandeen@xxxxxxxxxxx>, Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx>, Postfix users <postfix-users@xxxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <20081031225615.5E66B1F3EA0@xxxxxxxxxxxxxxxxxxx>
Mail-followup-to: Wietse Venema <wietse@xxxxxxxxxxxxx>, Eric Sandeen <sandeen@xxxxxxxxxxx>, Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx>, Postfix users <postfix-users@xxxxxxxxxxx>, xfs@xxxxxxxxxxx
References: <20081031221817.GD19509@disturbed> <20081031225615.5E66B1F3EA0@xxxxxxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
On Fri, Oct 31, 2008 at 06:56:15PM -0400, Wietse Venema wrote:
> Dave Chinner:
> Here's something I would like to know regarding the order of
> directory updates:
> 
> - Does fsync(file) guarantee the file's directory entry is safe?

No.

> Some file systems complete directory updates before the open/link/rename
> system call returns, so fsync() doesn't have to worry about it.

If you run with '-o dirsync', all directory transactions are guaranteed
to be in the log on disk by the time the syscall returns. Note that
this means you do at least one log write per create/link/rename/unlink
syscall, which has performance impact....

> - Does rename() guarantee that at least one directory entry will
> exist even when the system crashes in the middle of the operation?

Yes - either it will complete atomically or no change will occur at
all.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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