On Wed, Jan 14, 2009 at 2:40 PM, Mattias Pantzare <pantz...@gmail.com>wrote:
> On Wed, Jan 14, 2009 at 20:03, Tim <t...@tcsac.net> wrote: > > > > > > 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. > > ZFS will always flush the disk cache at appropriate times. If ZFS > thinks that is alone it will turn the write cache on the disk on. I'm not sure if you're trying to argue or agree. If you're trying to argue, you're going to have to do a better job than "zfs will always flush disk cache at appropriate times", because that's outright false in the case where zfs doesn't own the entire disk. That flush may very well produce an outcome zfs could never pre-determine. > > > It could cause corruption if you had UFS and zfs on the same disk. > > It is safe to have UFS and ZFS on the same disk and it has always been > safe. > ***unless you turn on write cache. And without write cache, performance sucks. Hence me answering the OP's question. > > Write cache on the disk is not safe for UFS, that is why zfs will turn > it on only if it is alone. Which is EXACTLY what he's asking, and what I just told him.
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