On Wed, Jun 9, 2010 at 9:20 AM, Geoff Nordli <geo...@grokworx.com> wrote: > Have you played with the flush interval? > > I am using iscsi based zvols, and I am thinking about not using the caching > in vbox and instead rely on the comstar/zfs side. > > What do you think?
If you care about your data, IgnoreFlush should always be set for all the drives. This ensure that a flush request from the guest actually writes data to disk. FlushInterval is a little different, in that it prevents the amount of buffered write data from from stalling the guest when the host finally does write it out. It's OK to let VBox cache some data if you have fast enough storage. If your storage is reasonably fast, you shouldn't need to touch FlushInterval. As far as my experience, my zpool is an 8 disk raidz2 comprised of 5400 rpm drives, so it's definitely at the low end of the performance spectrum. The OpenSolaris machine is hosting 3 linux guests in VirtualBox 3.0. Initially I was using disk images in a zfs filesystem. I was having trouble with IO failing stalling and guests remounting their disks read-only. Setting FlushInterval to 10MB (as recommended in the VBox manual) prevented the host from hanging but disk performance was still poor. I've moved to using raw disks mapped to zvols (/dev/zvol/rdsk) and removed the FlushInterval settings. The io stalls that I encountered using image files went away. -B -- Brandon High : bh...@freaks.com _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
