Tim writes: > On Tue, Jan 13, 2009 at 6:26 AM, Brian Wilson <bfwil...@doit.wisc.edu>wrote: > > > > > Does creating ZFS pools on multiple partitions on the same physical drive > > still run into the performance and other issues that putting pools in > > slices > > does? > > > > > Is zfs going to own the whole drive or not? The *issue* is that zfs will > not use the drive cache if it doesn't own the whole disk since it won't know > whether or not it should be flushing cache at any given point in time. >
> It could cause corruption if you had UFS and zfs on the same disk. > Let me correct a few things. ZFS unconditionaly flushes the write caches when it needs to and owning a drive or not is not important for the consistency of ZFS. If ZFS owns a disk it will enable the write cache on the drive but I'm not positive this has a great performance impact today. It used to but that was before we had a proper NCQ implementation. Today I don't know that it helps much. That this is because we always flush the cache when consistency requires it. The performance issue of using a drive to multiple unrelated consumers (ZFS & UFS) is that, if both are active at the same time, this will defeat the I/O scheduling smarts implemented in ZFS. Rather than have data streaming to some physical location of the rust, the competition of UFS for I/O will cause extra head movement. -r _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
