[Sheepdog] [PATCH] sheep: disable object cache by default

[Liu Yuan]

On 05/08/2012 01:48 AM, MORITA Kazutaka wrote:

> For example:
> 
>   $ qemu-img convert ~/linux.img sheepdog:linux
>   $ collie vdi read linux 0 512 | hd | head -1
>   00000000  fa eb 7c 6c 62 61 4c 49  4c 4f 01 00 15 04 09 00  |..|lbaLILO......|
>   $ qemu-img snapshot -c snap sheepdog:linux
>   $ collie vdi read linux 0 512 | hd | head -1
>   00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
> 
> We cannot read the correct data after snapshotting because the
> snapshot operation doesn't read the cached data.


I am surprised you didn't notice that qemu-img convert use 'unsafe' mode
as default, this means it tells sheepdog block driver NOT flush it at
all. So should we flush the cache even users asks us explicitly NOT to?

Again, to remind that qemu-img snapshot doesn't accept a -t option at
all for now.

Thanks,
Yuan