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Re: [Qemu-devel] Very poor IO performance which looks like some design p
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] Very poor IO performance which looks like some design problem. |
Date: |
Mon, 13 Apr 2015 15:53:10 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 |
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