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Re: [Qemu-devel] Default cache mode
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] Default cache mode |
Date: |
Wed, 29 Jun 2011 13:52:19 +0100 |
On Wed, Jun 29, 2011 at 12:59 PM, Kevin Wolf <address@hidden> wrote:
> I'm not entirely sure if I should suggest writeback or none as the new
> default, but I think it could make sense to change it.
I agree that cache=none is safe and fast with correct guests and local
disks. It is beaten by cache=writeback in cases where the host has a
lot of buffer cache to play with and the guest has very little - for
example when running qemu without a -m argument. If I was running
qemu-system-arm I might like cache=writeback. If I was virtualizing
x86 servers I might like cache=none.
cache=none as a default - which some management tools inherit - would
be reasonable. Folks using command-line qemu can always tweak to use
cache=writeback or even cache=unsafe if performance matters but data
integrity does not.
Whether it is safe to transition to cache=none or not depends on what
broken guests are still widely deployed. Does CentOS 5 flush the disk
cache?
Stefan
- Re: [Qemu-devel] Default cache mode, (continued)
Re: [Qemu-devel] Default cache mode, Alexander Graf, 2011/06/29
Re: [Qemu-devel] Default cache mode,
Stefan Hajnoczi <=
Re: [Qemu-devel] Default cache mode, Avi Kivity, 2011/06/29