Date: Thu, 19 Jan 2006 12:14:37 +0000 From: Gavin Atkinson <gavin.atkinson@ury.york.ac.uk> To: Larry Rosenman <ler@lerctr.org> Cc: freebsd-stable@freebsd.org Subject: RE: Gmirror'd SWAP: no dump? Message-ID: <1137672877.89997.8.camel@buffy.york.ac.uk> In-Reply-To: <006001c61cee$6d792d50$68c8a8c0@lerctr.org> References: <006001c61cee$6d792d50$68c8a8c0@lerctr.org>
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On Thu, 2006-01-19 at 05:49 -0600, Larry Rosenman wrote: > Igor Robul wrote: > > On Wed, Jan 18, 2006 at 12:44:27PM -0600, Larry Rosenman wrote: > >> Are there any plans to support dumping to a gmirror'd swapfile? > > Dumping occurs when kernel is in "bad condition", so GEOM can not be > > safe used (for example panic in GEOM code). > > > > Check archives for last month of 2005 for longer explanation. > > I was afraid of that. What's the recommendation for how to > Set up a 2-disk system with mirroring then? > > All the HOWTO's I've seen have the entire disk mirrored, including > all the pieces. > > My current setup is 3 BSD partitions in 1 FDISK slice. With the entire > disk (da0/da1) mirrored. > > How can I set it up to allow dumps? If you look at the mirror status, you'll see each disk is assigned a priority. In theory, "The component with the biggest priority is used [...] as a master component when resynchronization is needed, e.g. after a power failure when the device was open for writing." (gmirror(8)). Therefore, if you set dumps to /dev/da0s1b (or whichever swap partition is on the disk with the biggest priority), the machine can dump to the disk directly, and will end up resyncing to the other disk on reboot (which it would have had to do anyway due to the panic), and your dump will be doubly safe. I say "in theory", because on the one machine I have that uses gmirror, both disks have a priority of zero (which i get the feeling is invalid, from the gmirror man page). Gavin
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