On Tue, 2 Dec 2014 08:41:11 +1100 NeilBrown <neilb@xxxxxxx> wrote: > On Mon, 1 Dec 2014 16:19:47 -0500 Joe Lawrence <joe.lawrence@xxxxxxxxxxx> > wrote: > > > On Thu, 27 Nov 2014 07:41:58 +1100 > > NeilBrown <neilb@xxxxxxx> wrote: > > > > > On Mon, 24 Nov 2014 23:07:32 -0500 Joe Lawrence <joe.lawrence@xxxxxxxxxxx> > > > wrote: > > > > > > > Does anyone know how its possible to determine which side of an LVM RAID 1 > > > > is the stale partner during RAID resync? > > > > > > > > In ordinary MD RAID, I believe you can check > > > > /sys/block/md0/md/dev-XXX/state, > > > > > > Why do you believe that? > > > > > > During a resync (after an unclean shutdown) the devices are indistinguishable. > > > RAID1 reads all drives and if there is a difference it chooses one data block > > > to write to the others - always the one with the lowest index number. > > > > > > So with md or LVM it is the same: first "first" is "copied" to the "second". > > > > Hi Neil, > > > > Here's a quick example of my thought-process, where md2 is an in-sync > > RAID1 of sdq2 and sdr2 with an internal write bitmap: > > > > % mdadm --fail /dev/md3 /dev/sdr2 > > % mdadm --remove /dev/md3 /dev/sdr2 > > You are referring to what I would call "recovery", not "resync" > (which is why I put "(after an unclean shutdown)" in my answer to make it > clear what circumstances I was talking about). > > resync: fixing things after an unclean shutdown > recovery: restoring data after a device has been removed an another > (or possibly the same) added. > > I think > > dmsetup info > > should provide the info you want. > One of the fields is a sequence of letters 'D', 'a', 'A'. > > * Status characters: > * 'D' = Dead/Failed device > * 'a' = Alive but not in-sync > * 'A' = Alive and in-sync > > Does that provide the information you wanted? Yes! When I add a disk back to the array, I see the status characters you mentioned during _recovery_: % while [ true ] do dmsetup status vg0-lvraid0 sleep 10s done 0 18857984 raid raid1 2 DA 18857984/18857984 idle 0 0 18857984 raid raid1 2 DA 18857984/18857984 idle 0 0 18857984 raid raid1 2 DA 18857984/18857984 idle 0 0 18857984 raid raid1 2 aA 0/18857984 recover 0 0 18857984 raid raid1 2 aA 0/18857984 recover 0 0 18857984 raid raid1 2 aA 256/18857984 recover 0 0 18857984 raid raid1 2 aA 8519680/18857984 recover 0 0 18857984 raid raid1 2 AA 18857984/18857984 idle 0 So now, determining which disk is which in the raid_set. Can I use a command like lvs to tie the n-th character status back to a device? % lvs -a -o name,devices vg0 LV Devices lvraid0 lvraid0_rimage_0(0),lvraid0_rimage_1(0) [lvraid0_rimage_0] /dev/sdr1(1) [lvraid0_rimage_1] /dev/sdt1(1) [lvraid0_rmeta_0] /dev/sdr1(0) [lvraid0_rmeta_1] /dev/sdt1(0) Where the first character represents [lvraid0_rimage_0] and the second [lvraid0_rimage_1]. Thanks, -- Joe -- 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
