On Mon, 28 Jan 2013 11:40:53 +0200 Volodymyr Kostyrko <[email protected]> wrote:
> 28.01.2013 09:03, Steve O'Hara-Smith: > > On Sun, 27 Jan 2013 22:05:05 -0800 > > Michael Sierchio <[email protected]> wrote: > > > >> On Sun, Jan 27, 2013 at 5:36 PM, Shane Ambler <[email protected]> > >> wrote: > >> > >>> I recall reading that using partitions for zfs on FreeBSD was as good > >>> as full disks. > >> > >> No, it isn't - ZFS can fully utilize disk caches when presented with > >> whole devices. There are possible reasons to create partitions - one > >> being that if an unfriendly OS sees the device, it won't try to > >> initialize it if it sees a partition map. Another is using a cheap > >> RAID controller that can't be fully disabled - in which case you > >> generally need to create a partition that doesn't include the last few > >> sectors of the disk, where such controllers keep magic data. > > > > There's one other good reason to use partitions when mirroring. > > When the time comes to replace a drive in a mirror it is necessary that > > the new drive be the same size (or larger) than the one it replaces. > > Given that drives of nominally the same capacity (and even of the same > > type and brand bought at different times) tend not to be exactly the > > same size using a partition a little smaller than the whole drive makes > > it certain that a replacement drive will be big enough to use in the > > mirror when it arrives. > > There's no need for that as ZFS can use same or bigger partition to > mirror existing one. If the second one would be smaller - do some math > and cut out some swap space. The problem arises when a drive fails, you order a replacement (go down the shop whatever) and when the new disc arrives and it's a few blocks smaller than the existing one. Then it cannot be used to mirror the existing one and you're in for a messy job to get a working mirror up. -- Steve O'Hara-Smith <[email protected]> _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[email protected]"
