Thanks; I didn't know one could do that. But am I correct in my understanding that if 2 arrays have the same homehost they will have the same end (last half?) of the UUID? That would mean the 2 devices I'm looking at can't have the same homehost. I am able to guess the homehost for one of them using your trick; none of the possibilities have tried have matched the other. Ross ________________________________________ From: NeilBrown [neilb@xxxxxxx] Sent: Monday, November 24, 2014 7:08 PM To: Boylan, Ross Cc: linux-raid@xxxxxxxxxxxxxxx Subject: Re: homehost and 0.90 format On Tue, 11 Nov 2014 03:14:34 +0000 "Boylan, Ross" <Ross.Boylan@xxxxxxxx> wrote: > I am trying to figure out which of my RAID devices is considered home. I haven't switched machines, but I have several operating systems, with different hostnames, on the machine. 0.90 format metadata. > > Even 2 RAID devices created on the same OS don't seem to have any UUID in common. i thought that the end of the UUID's would be the same. For example, inhttp://marc.info/?l=linux-raid&m=123999237229707 Neil Brown says > > Note that 0.90 metadata does contain homehost information to some > > extent. When homehost is set, the last few bytes of the uuid is set > > from a hash of the homehost name. That makes it possible to test if a > > 0.90 array was created for 'this' host, but not to find out what host > > it was created for. > > mdadm.conf has > HOMEHOST <system> > > The 2 UUIDS are > 8691ad98:af955756:ae5efbfa:dfd20ce6 > 6d89d3b5:19a0acce:319e1a9c:58606385 > > Thanks, > Ross Boylan You need to guess-and-test. e.g. mdadm --detail /dev/md7 --homehost=foo | grep UUID If it says "(local to host foo)", then "foo" is the correct name. If not, then try a different name. NeilBrown > > Details: > > root@wheezy4:~# mdadm --detail /dev/md7 > /dev/md7: > Version : 0.90 > Creation Time : Fri Oct 3 17:20:13 2014 > Raid Level : raid1 > Array Size : 48828352 (46.57 GiB 50.00 GB) > Used Dev Size : 48828352 (46.57 GiB 50.00 GB) > Raid Devices : 1 > Total Devices : 1 > Preferred Minor : 7 > Persistence : Superblock is persistent > > Update Time : Tue Nov 4 17:48:40 2014 > State : clean > Active Devices : 1 > Working Devices : 1 > Failed Devices : 0 > Spare Devices : 0 > > UUID : 8691ad98:af955756:ae5efbfa:dfd20ce6 > Events : 0.1 > > Number Major Minor RaidDevice State > 0 8 20 0 active sync /dev/sdb4 > root@wheezy4:~# mdadm --detail /dev/md8 > /dev/md8: > Version : 0.90 > Creation Time : Tue Sep 30 13:27:56 2014 > Raid Level : raid1 > Array Size : 970702784 (925.73 GiB 994.00 GB) > Used Dev Size : 970702784 (925.73 GiB 994.00 GB) > Raid Devices : 2 > Total Devices : 1 > Preferred Minor : 8 > Persistence : Superblock is persistent > > Update Time : Mon Nov 10 18:16:11 2014 > State : clean, degraded > Active Devices : 1 > Working Devices : 1 > Failed Devices : 0 > Spare Devices : 0 > > UUID : 6d89d3b5:19a0acce:319e1a9c:58606385 > Events : 0.790792 > > Number Major Minor RaidDevice State > 0 8 19 0 active sync /dev/sdb3 > 1 0 0 1 removed > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
