From: Mike Waychison <Michael.Waychison@Sun.COM>
To: Kenny Simpson <theonetruekenny@yahoo.com>
Cc: autofs@linux.kernel.org
Subject: Re: Performance of autofs/amd-managed directory
Date: Wed, 26 May 2004 08:47:09 -0400 [thread overview]
Message-ID: <40B491CD.1070707@sun.com> (raw)
In-Reply-To: <20040526030234.47115.qmail@web20025.mail.yahoo.com>
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Kenny Simpson wrote:
> What is the performance penalty for write access to files in a managed
> directory vs. a fstab entry?
> I have a program that is very sensitive to write latency, and am being
> pressured to use amd or automount to access a NAS instead of my trusty
fstab
> entry.
>
> My app uses a transactional log file that resides on a NAS. I'd
prefer to keep
> a simple fstab entry and use O_DIRECT to access the file, but if there
is no
> penalty, I would switch. Does O_DIRECT have meaning for automount or
> amd-managed files? (isn't amd user-space, so it would need to copy data
> anyway?)
>
As Ian already pointed out, automount simply mounts filesystems in place
when requested and does not affect any file access fast-paths.
Similarly, amd also simply mounts the NFS filesystems, albeit in a
different location and uses symlinks to redirect the user. This has the
side-effect that a chdir('..') will drop you in a different directory.
As long as you have O_DIRECT support in your NFS client, neither
solution will have any real adverse effects on your transactional log.
- --
Mike Waychison
Sun Microsystems, Inc.
1 (650) 352-5299 voice
1 (416) 202-8336 voice
mailto: Michael.Waychison@Sun.COM
http://www.sun.com
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NOTICE: The opinions expressed in this email are held by me,
and may not represent the views of Sun Microsystems, Inc.
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prev parent reply other threads:[~2004-05-26 12:47 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-05-26 3:02 Performance of autofs/amd-managed directory Kenny Simpson
2004-05-26 5:28 ` Ian Kent
2004-05-26 12:47 ` Mike Waychison [this message]
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