[linux-lvm] Mirror resync direction
Paul LeoNerd Evans
leonerd-lvm at leonerd.org.uk
Thu Oct 26 20:17:38 UTC 2006
I'm running kernel 2.6.17 using the lvm2 package currently in debian
testing (2.02.06-3). I use it to set up a VG containing two
PVs, /dev/sda2 and /dev/sdb2. I create a mirror LV using corelog:
lvcreate --mirror 1 --corelog ...
I create a filesystem on it, and populate it with files. I then try
testing how it copes with drive failures, by simulating a replaced disk.
To do this, I zero out one of the sides using
dd if=/dev/zero of=/dev/sda2
Having done that, I do the usual restore method
pvcreate --uuid 'whatever' /dev/sda2
vgchange -a y
And I note that it starts to resync the mirror. But it goes in the
"wrong" direction - sda2's PV is the master, but that's been zeroed out.
sdb2's is the slave but contains the real data. The block copying goes in
the wrong direction here, copying the master's zeroes over the good data
in the slave.
Is this a bug in the LVM2 tools, or the dm-mirror target, or what? Is it
perhaps a limitation of --corelog; in which case, how can I protect
Paul "LeoNerd" Evans
leonerd at leonerd.org.uk
ICQ# 4135350 | Registered Linux# 179460
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