On 08/26/2009 03:06 PM, Rusty Russell wrote:
On Tue, 25 Aug 2009 11:46:08 pm Christoph Hellwig wrote:
On Tue, Aug 25, 2009 at 11:41:37PM +0930, Rusty Russell wrote:
On Fri, 21 Aug 2009 06:26:16 am Christoph Hellwig wrote:
Currently virtio-blk doesn't set any QUEUE_ORDERED_ flag by default, which
means it does not allow filesystems to use barriers. But the typical use
case for virtio-blk is to use a backed that uses synchronous I/O
Really? Does qemu open with O_SYNC?
I'm definitely no block expert, but this seems strange...
Rusty.
Qemu can open it various ways, but the only one that is fully safe
is O_SYNC (cache=writethrough).
(Rusty goes away and reads the qemu man page).
By default, if no explicit caching is specified for a qcow2 disk image,
cache=writeback will be used.
It's now switched to writethrough. In any case, cache=writeback means
"lie to the guest, we don't care about integrity".
Are you claiming qcow2 is unusual? I can believe snapshot is less common,
though I use it all the time.
You'd normally have to add a feature for something like this. I don't
think this is different.
Why do we need to add a feature for this?
--
error compiling committee.c: too many arguments to function
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