I am running a 6.3 system and have had various problems with disk reliability on a key filesystem, probably down to SCSI hardware or drivers. I'm intending to replace that SCSI disk with a pair of SATA disks ad6/7, using gmirror as gm0 (while keeping ad4 as our boot disk). I have set up the mirror and right now I'm part-way through using rsync to transfer the data. But I have a question concerning the underlying operation of GEOM, which is troubling me. I have read the various man pages and handbook pages relating to GEOM and gmirror, but they don't seem to answer this.
When I reboot the system, gmirror comes up (because of the line in /boot/loader.conf) and gm0 appears, backed by ad6/7. Where is this configuration information stored? That is, how does the system know to make gm0, with ad6/7 as the backing store. I would expect there to be a file somewhere in /etc with this config information, but I don't see it in the documentation. From reading gmirror(8), I understand that there is a label sector at the ends of ad6 and ad7, identifying them as parts of gm0. But that config information is back-to-front: at boot time the system knows from /etc/fstab that it needs gm0; how does it find the underlying disks? Does the system search the ends of all physically-attached disks, looking for GEOM labels, and automatically make any corresponding GEOM devices? Surely not (that would mean, for instance, that if I took one of these disks out of this machine and put it into another FreeBSD system then that machine would automatically set up gm0 with this disk). Possibly I'm just being dense. Can someone enlighten me? Nick Barnes Ravenbrook Limited _______________________________________________ email@example.com mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"