Since RHEL 6.4, the "-type raid*" options of lvcreate have been
disabled for a clvm setup. Which is ok for me, since I don't like the
chance of haveing data corruption.
However: when needing to do a mirror between 2 SAN storages, something
is still needed. So I use the good old "-m 1" and cmirrord. And here
lies the problem: suppose I have 2 disks from SAN 1, and 2 disks from
SAN 2 so that I need to stripe over the SAN 1 disks and then mirror to
SAN 2 disks.
This command (combining stripe and mirror) is working as expected:
lvcreate -m1 -i 2 -I 4 --nosync --alloc anywhere -n lvtest vgtest -L
90G /dev/mapper/CLVM-SAN1-1315 /dev/mapper/CLVM-SAN1-1316
/dev/mapper/CLVM-SAN2-1415 /dev/mapper/CLVM-SAN2-14
The command "lvs -a -o +devices" shows the setup is as expected:
lvtest vgtest Mwa-a-m-- 90.00g
lvtest_mlog 100.00 lvtest_mimage_0(0),lvtest_mimage_1(0)
[lvtest_mimage_0] vgtest iwa-aom-- 90.00g
/dev/mapper/CLVM-SAN1-1315(0),/dev/mapper/CLVM-SAN1-1316(0)
[lvtest_mimage_1] vgtest iwa-aom-- 90.00g
/dev/mapper/CLVM-SAN2-1415(0),/dev/mapper/CLVM-SAN2-1416(0)
[lvtest_mlog] vgtest lwa-aom-- 4.00m
/dev/mapper/CLVM-SAN2-1416(11520)
The command "pvs -a -o +devices" shows everything is ok (the mirror leg
is also striped, since there's some space free on both the mirrored
devices):
PV VG Fmt Attr PSize PFree
Devices
/dev/mapper/CLVM-SAN1-1315 vgtest lvm2 a-- 50.00g 5.00g
/dev/mapper/CLVM-SAN1-1315(0),/dev/mapper/CLVM-SAN1-1316(0)
/dev/mapper/CLVM-SAN1-1315 vgtest lvm2 a-- 50.00g 5.00g
/dev/mapper/CLVM-SAN1-1316 vgtest lvm2 a-- 50.00g 5.00g
/dev/mapper/CLVM-SAN1-1315(0),/dev/mapper/CLVM-SAN1-1316(0)
/dev/mapper/CLVM-SAN1-1316 vgtest lvm2 a-- 50.00g 5.00g
/dev/mapper/CLVM-SAN2-1415 vgtest lvm2 a-- 50.00g 5.00g
/dev/mapper/CLVM-SAN2-1415(0),/dev/mapper/CLVM-SAN2-1416(0)
/dev/mapper/CLVM-SAN2-1415 vgtest lvm2 a-- 50.00g 5.00g
/dev/mapper/CLVM-SAN2-1416 vgtest lvm2 a-- 50.00g 4.99g
/dev/mapper/CLVM-SAN2-1415(0),/dev/mapper/CLVM-SAN2-1416(0)
/dev/mapper/CLVM-SAN2-1416 vgtest lvm2 a-- 50.00g 4.99g
/dev/mapper/CLVM-SAN2-1416(11520)
/dev/mapper/CLVM-SAN2-1416 vgtest lvm2 a-- 50.00g 4.99g
Now, however, if I decide to first create the stripe on SAN1:
lvcreate -i 2 -I 4 -n lvtest vgtest -L 90G /dev/mapper/CLVM-SAN1-1315
/dev/mapper/CLVM-SAN1-1316
and then the mirror (mirrorlog core used for testing):
lvconvert -m1 --mirrorlog core vgtest/lvtest
The mirrored leg is now not striped:
/dev/mapper/CLVM-SAN1-1315 vgtest lvm2 a-- 50.00g 5.00g
/dev/mapper/CLVM-SAN1-1315(0),/dev/mapper/CLVM-SAN1-1316(0)
/dev/mapper/CLVM-SAN1-1315 vgtest lvm2 a-- 50.00g 5.00g
/dev/mapper/CLVM-SAN1-1316 vgtest lvm2 a-- 50.00g 5.00g
/dev/mapper/CLVM-SAN1-1315(0),/dev/mapper/CLVM-SAN1-1316(0)
/dev/mapper/CLVM-SAN1-1316 vgtest lvm2 a-- 50.00g 5.00g
/dev/mapper/CLVM-SAN2-1415 vgtest lvm2 a-- 50.00g 0
/dev/mapper/CLVM-SAN2-1415(0)
/dev/mapper/CLVM-SAN2-1416 vgtest lvm2 a-- 50.00g 9.99g
/dev/mapper/CLVM-SAN2-1416(0)
/dev/mapper/CLVM-SAN2-1416 vgtest lvm2 a-- 50.00g 9.99g
In itself this is not a problem, but when the mirror breaks and you
need to recreate it, the same command needs to be executed. Suppose in
the beginning we execute the lvcreate with stripe/mirror combo and we
need to rebuild the mirror after a failure, suddenly one part will no
longer be striped.
So here are my questions:
- Is there an option to lvconvert to also force the same striping on
the mirror leg?
- And a second question: "-mirrorlog mirrored" doesn't seem to be
possible in a clvm setup, is this intended?
- And in general: is there another method to get a mirrored stripe in a
clustered setup?
With friendly regards,
Franky
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