Removing LVM
So, since I’m sick of LVM, and I have another couple TB of disks to add to my file server, I thought now would be a good time as ever to remove LVM, and go to straight linear raid over mirrors.
Step 1: Back up old data:
I’ll make my new linear raid, over my new disks. I can then make my new XFS partition on that, back my old stuff up, swap it, remove LVM, and then add my old mirrors to my new linear partition.
root@central:~# mdadm --create /dev/md3 --level=mirror -n 2 /dev/sdc /dev/sdf
mdadm: Note: this array has metadata at the start and
may not be suitable as a boot device. If you plan to
store '/boot' on this device please ensure that
your boot-loader understands md/v1.x metadata, or use
--metadata=0.90
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md3 started.
root@central:~# mdadm --create /dev/md100 --force --level=linear -n 1 /dev/md3
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md100 started.
root@central:~# mkfs.xfs /dev/md100
meta-data=/dev/md100 isize=256 agcount=4, agsize=91571025 blks
= sectsz=512 attr=2
data = bsize=4096 blocks=366284100, imaxpct=5
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0
log =internal log bsize=4096 blocks=178849, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
root@central:~# mount /dev/md100 /mnt
root@central:~# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/vg--md--all-data--xfs
943667200 552745476 390921724 59% /data
/dev/md100 1464421004 4256 1464416748 1% /mnt
root@central:~# cat /proc/mdstat
Personalities : [raid1] [linear]
md100 : active linear md3[0]
1465136400 blocks super 1.2 0k rounding
[... snip ...]
md3 : active raid1 sdf[1] sdc[0]
1465137424 blocks super 1.2 [2/2] [UU]
[>....................] resync = 3.8% (56198208/1465137424) finish=241.5min speed=97207K/secA couple hours of rsync running on top of the rebuild, and we’re up:
root@central:/# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg--md--all-data--xfs
900G 528G 373G 59% /data
/dev/md100 1.4T 537G 860G 39% /mntInspection showed that the extra disk space came from 2 sources, me leving -H and -S off the rsync. I checked, and by syncing small portions of the tree, with -H and -S, their sizes matched, but really, a couple of gigs isn’t work a whole resync.
Step 2: Remove LVM
I’ve been waiting for this step for a few years know. Since my data is now on my my new XFS filesystem, all I need to do is switch to the new one, and remove LVM:
root@central:/# mkdir /data.old
root@central:/# mount --move /data /data.old
root@central:/# mount --move /mnt /data
root@central:/# umount /data.old
root@central:/# invoke-rc.d lvm2 stop
Shutting down LVM Volume Groups 0 logical volume(s) in volume group "vg-md-all" now active
.
root@central:/# dpkg --purge lvm2
(Reading database ... 46953 files and directories currently installed.)
Removing lvm2 ...
Purging configuration files for lvm2 ...
dpkg: warning: while removing lvm2, directory '/etc/lvm' not empty so not removed.
Processing triggers for man-db ...
root@central:/# And just to make sure:
root@central:/# dd if=/dev/zero of=/dev/md0
^C
190513+0 records in
190513+0 records out
97542656 bytes (98 MB) copied, 10.8053 s, 9.0 MB/s
root@central:/# dd if=/dev/zero of=/dev/md1
^C
273273+0 records in
273273+0 records out
139915776 bytes (140 MB) copied, 8.44314 s, 16.6 MB/s
root@central:/#Yes, I really don’t like LVM.
Step 3: Clean up old mirrors
MD set md1 is my pair of small 160GB disks. I’m going to break thtt up, and use those 2 disks for “expermients”.
root@central:/# mdadm --stop /dev/md0
mdadm: stopped /dev/md0
root@central:/# cat /proc/mdstat
Personalities : [raid1] [linear]
md100 : active linear md3[0]
1465136400 blocks super 1.2 0k rounding
md3 : active raid1 sdf[1] sdc[0]
1465137424 blocks super 1.2 [2/2] [UU]
md1 : active raid1 sdb[0] sde[1]
976762496 blocks [2/2] [UU]
unused devices: <none>
root@central:/# mdadm --zero-superblock /dev/sda /dev/sddNow md1 is my pair of 1TB disks, but that was made old old mdadm, and has old superblock version. Supposedly superblock version 1.2 is better for filesystems aligning to sectors underneath. So let’s change it, then add it to our linear array:
root@central:/# mdadm --stop /dev/md1
mdadm: stopped /dev/md1
root@central:/# mdadm --zero-superblock /dev/sdb /dev/sde
root@central:/# mdadm --create /dev/md0 --name central:mirror-1TB --assume-clean --level=mirror -n 2 /dev/sdb /dev/sde
mdadm: Note: this array has metadata at the start and
may not be suitable as a boot device. If you plan to
store '/boot' on this device please ensure that
your boot-loader understands md/v1.x metadata, or use
--metadata=0.90
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.Step 4: Extend our linear set
Because this was the whole point (well, besides getting rid of LVM):
root@central:/# mdadm /dev/md100 --grow --add /dev/md0
root@central:/# cat /proc/mdstat
Personalities : [raid1] [linear]
md0 : active raid1 sde[1] sdb[0]
976761424 blocks super 1.2 [2/2] [UU]
md100 : active linear md0[1] md3[0]
2441896800 blocks super 1.2 0k rounding
md3 : active raid1 sdf[1] sdc[0]
1465137424 blocks super 1.2 [2/2] [UU]
unused devices: <none>
root@central:/# grep md100 /proc/partitions
9 100 2441896800 md100And now, of course, we need to extend XFS:
root@central:/# xfs_growfs /data
meta-data=/dev/md100 isize=256 agcount=4, agsize=91571025 blks
= sectsz=512 attr=2
data = bsize=4096 blocks=366284100, imaxpct=5
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0
log =internal bsize=4096 blocks=178849, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
data blocks changed from 366284100 to 610474200
root@central:/# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/md100 2.3T 538G 1.8T 24% /dataStep 5: Final configuration
And, before you quit, make sure to touchup /etc/mdadm/mdadm.conf:
mdadm -Es >> /etc/mdadm/mdadm.conf
vi /etc/mdadm/mdadm.confAnd since I’ve got a new FS for my /data, I need to remember to update fstab:
/dev/disk/by-id/md-uuid-0bdd41ba:e402e25a:dc8404a6:5f7db4d5 /data xfs defaults 0 0