From: "J. Bruce Fields" <bfields@fieldses.org>
To: Alexandre Depoutovitch <adepoutovitch@vmware.com>
Cc: linux-nfs@vger.kernel.org
Subject: Re: About Direct I/O
Date: Fri, 16 Mar 2012 16:35:21 -0400 [thread overview]
Message-ID: <20120316203521.GA22929@fieldses.org> (raw)
In-Reply-To: <6866525b.00001bd8.0000023d@aldep-VC.vmware.com>
On Fri, Mar 16, 2012 at 11:14:04AM -0700, Alexandre Depoutovitch wrote:
> Hello,
> I am trying to do random sector aligned writes to an NFS mounted disk. The
> performance is order of magnitude worse than 4K (file system block size)
> aligned I/O.
> The reason is that NFS demon (Linux kernel 2.6.32) on the server side
> always does buffered I/O, which behaves poorly for block unaligned
> requests.
> Is there a way to tell NFS daemon to use direct I/O?
No.
> If not, is it an implementation limitation or there is a fundamental
> problem with using direct I/O in NFS server?
I'm shamefully ignorant of Direct IO....
If we supported Direct IO, are there heuristics that would let the
server figure out on its own when it helped and when it didn't? Or
would the administrator be stuck trying to figure that out?
Is Direct IO possible from kernel buffers these days? Are there
alignment restrictions?
--b.
next prev parent reply other threads:[~2012-03-16 20:35 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-15 20:23 About pNFS installation process Bruno Silva
2012-03-16 0:16 ` Jim Rees
2012-03-16 18:14 ` About Direct I/O Alexandre Depoutovitch
2012-03-16 20:35 ` J. Bruce Fields [this message]
2012-03-16 20:58 ` Myklebust, Trond
2012-03-18 10:51 ` About pNFS installation process Lev Solomonov
2012-03-23 17:21 ` Bruno Silva
2012-03-23 18:02 ` Jim Rees
2012-04-04 0:20 ` Lev Solomonov
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