On Fri, Feb 17, 2012 at 3:12 AM, Pete French <petefre...@ingresso.co.uk> wrote: >> I wasn't aware you could do that. I was only aware that it was the >> other way around. That (my) misconception seems to also be relayed >> by others such as Miroslav who said: > > Should this not be the recommended way of doing things even for MBR > disks ? I have a lot of machines booting from gmirror, but we always > do it by mirroring MBR partitions (or GPT ones). I cant see why you would > want to do it the other way round in fact. It doesnt gain you anything > does it ?
The problem with mirroring partitions is that you thrash the disk during the rebuild after replacing a failed disk. And the more partitions you have, the worse it gets. If you mirror the device, then the rebuild process only has to rebuild a single "thing". If you mirror 4 partitions on a device, then there will be four simultaneous, parallel rebuild processes running, thrashing the drive heads on both devices, killing you I/O throughput and extending the length of the rebuild. And if you mix your redundancy technologies (like gmirror and zfs mirror) it gets even worse due to competing rebuild schedulers. -- Freddie Cash fjwc...@gmail.com _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"
