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Re: [Qemu-devel] [PATCH] block: add cache=directsync parameter to -drive


From: Kevin Wolf
Subject: Re: [Qemu-devel] [PATCH] block: add cache=directsync parameter to -drive
Date: Wed, 03 Aug 2011 17:22:28 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:5.0) Gecko/20110707 Thunderbird/5.0

Am 01.08.2011 11:39, schrieb Stefan Hajnoczi:
> This patch adds -drive cache=directsync for O_DIRECT | O_SYNC host file
> I/O with no disk write cache presented to the guest.
> 
> This mode is useful when guests may not be sending flushes when
> appropriate and therefore leave data at risk in case of power failure.
> When cache=directsync is used, write operations are only completed to
> the guest when data is safely on disk.
> 
> This new mode is like cache=writethrough but it bypasses the host page
> cache.
> 
> Signed-off-by: Stefan Hajnoczi <address@hidden>

qemu-img has another parser for cache options that must be changed. This
should probably be refactored to a single implementation in block.c.

Kevin



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