Re: [kvm-devel] [PATCH] qemu: use statically allocate 512 byte buffer in the stack for sector in bdrv_commit

[Laurent V. <Lau...@bu...>]

Le lundi 07 janvier 2008 =C3=A0 10:34 -0500, Javier Guerra a =C3=A9crit :
> On 1/7/08, Laurent Vivier <Lau...@bu...> wrote:
> > What I'm wondering now is: is it really useful to have "cache=3Doff" an=
d
> > "snapshot=3Don" at the same time ?
>=20
> does "cache=3Doff" means disk cache? if so, it might be useful to test
> clustering filesystems.

"cache=3Doff" means files is opened with "O_DIRECT" and thus there is no
cache in the kernel memory on the host side.
IMO, "cache=3Doff" and "snapshot=3Don" are incompatible because a snapshot
can be seen like a cache.

> so far, the only way is to setup a network block device (iSCSI, AoE,
> nbd). i'd like to simply specify the same backing file for two
> instances' hdb parameter.

I'm sorry but I don't understand this part.

> and snapshots help a lot to go back after blowing up the on-disk structur=
es

But I think if you use a snapshot there is no reason to use "cache=3Doff"

Laurent
--=20
----------------- Lau...@bu...  ------------------
  "La perfection est atteinte non quand il ne reste rien =C3=A0
ajouter mais quand il ne reste rien =C3=A0 enlever." Saint Exup=C3=A9ry