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From: Paolo Bonzini <pbonzini@redhat.com>
To: ein <ein.net@gmail.com>, qemu-devel <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] Very poor IO performance which looks like some design problem.
Date: Mon, 13 Apr 2015 15:53:10 +0200	[thread overview]
Message-ID: <552BCA46.7010208@redhat.com> (raw)
In-Reply-To: <552BB682.6070707@gmail.com>



On 13/04/2015 14:28, ein wrote:
> 
> 
> Check out my update please:
> http://lists.nongnu.org/archive/html/qemu-devel/2015-04/msg01318.html
> 
> Using aio=native,cache=none results in 500%-2000% performance drop
> comparing to bare metal and 300%-1000% comparing to
> aio=threads,cache=unsafe.

Not a surprise that aio=threads,cache=unsafe is faster.  With
cache=unsafe you're telling QEMU that it's okay to lose data in case of
a host power loss.  Same for ext2 over XFS (ext2 isn't even journaled!).

Thus, use XFS and preallocate storage using the "fallocate" command.

Paolo

  reply	other threads:[~2015-04-13 13:53 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-10 20:38 [Qemu-devel] Very poor IO performance which looks like some design problem ein
2015-04-11 13:09 ` Paolo Bonzini
2015-04-11 17:10   ` ein
2015-04-11 19:00     ` ein
2015-04-13  1:45 ` Fam Zheng
2015-04-13 12:28   ` ein
2015-04-13 13:53     ` Paolo Bonzini [this message]
2015-04-14 10:31     ` Kevin Wolf

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