On Wed, Jun 29, 2011 at 3:13 PM, Anthony Liguori <anth...@codemonkey.ws> wrote: > On 06/29/2011 08:50 AM, Christoph Hellwig wrote: >> >> On Wed, Jun 29, 2011 at 07:23:31AM -0500, Anthony Liguori wrote: >>> >>> Which file system on the host? >> >> Any filesystem. Although extN and btrfs are particularly bad. >> >>> At any rate, I'm a big fan of making wce tunable in the guest and then I >>> think setting wce=1 is quite reasonable to do by default. >> >> Note that this means a manual override during each boot. Windows and >> modern Linux just use what's available. Only Solaris with ZFS actually >> turns WCE on if it's not set AFAIK. And to me it's a rather questionable >> behaviour at least for SCSI disks where the admin might have chosen >> those intentionally. (unlike ATA disks SCSI allows to store the setting >> permanently) > > Is WCE ever persisted by a disk? Would it make sense to have a mechanism to > persist the WCE setting for a guest?
Disks may store it in non-volatile memory, but it depends on the disk and is reported in the cache mode page for SCSI. Stefan
