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From: | Anthony Liguori |
Subject: | Re: [Qemu-devel] Re: [PATCH v2 6/7] qed: Read/write support |
Date: | Wed, 13 Oct 2010 09:08:17 -0500 |
User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.12) Gecko/20100915 Lightning/1.0b1 Thunderbird/3.0.8 |
On 10/13/2010 09:07 AM, Stefan Hajnoczi wrote:
That means we can maintain the physical size without introducing additional fsync()s in the allocation path. Since we're already writing out the header anyway, the write operation is basically free too.I don't see how it is free. It's an extra write. The good news is that it's very easy to amortize.We only need to update the header field on disk when we're already updating the header, so it's not even an extra write operation.
Because we're already writing out the sector that contains that field in the header.
Regards, Anthony Liguori
Stefan
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