I'm trying to move my root partition to raid based physical volumes, and I seem to be failing.
The procedure I'm using is somewhat complicated, but that's because my hosting provider has very limited installation capabilities, so I can't start with root filesystem made using lvm on raid volumes.
To test my case, I created virtual instance in VirtualBox, with 4 disks:
- /dev/sda - 8GB
- /dev/sdb - 8GB
- /dev/sdc - 20GB
- /dev/sdd - 20GB
And installed there Linux (Debian 8.5). Initially, after installation, layout is:
- /dev/sd[bcd] - not partitioned, not used
- /dev/sda - have 1 partition (/dev/sda1), small (4GB), used as PV for LVM
- on this PV, I created VG, and LV, which is now used as /:
This is how it looks:
=# mount /
mount: /dev/mapper/vg-root is already mounted or / busy
=# lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
root vg -wi-ao---- 3.72g
=# vgs
VG #PV #LV #SN Attr VSize VFree
vg 1 1 0 wz--n- 3.72g 0
=# pvs
PV VG Fmt Attr PSize PFree
/dev/sda1 vg lvm2 a-- 3.72g 0
Now, what I need/want, is to create couple of raids on small and large disks, and put / on them.
So, first I create the partitions. Since I will need to repartition /dev/sda, it's intermediary layout, and it looks like this:
=# for a in /dev/sd[abcd]; do fdisk -l $a; done | grep ^/
/dev/sda1 * 2048 7813119 7811072 3.7G 8e Linux LVM
/dev/sdb1 2048 16777215 16775168 8G fd Linux raid autodetect
/dev/sdc1 2048 16777215 16775168 8G fd Linux raid autodetect
/dev/sdc2 16777216 41943039 25165824 12G fd Linux raid autodetect
/dev/sdd1 2048 16777215 16775168 8G fd Linux raid autodetect
/dev/sdd2 16777216 41943039 25165824 12G fd Linux raid autodetect
Then, I make raid1 on the /dev/sd[cd]2 partitions:
=# mdadm -C /dev/md0 -l 1 --raid-devices 2 /dev/sd[cd]2
This made me /dev/md0, which I will use as temporary place for / filesystem:
=# pvcreate /dev/md0
=# vgextend vg /dev/md0
=# pvmove /dev/sda1 /dev/md0
=# vgreduce vg /dev/sda1
=# pvremove /dev/sda1
At this time, /dev/sda is free, so I can repartition it, to exact specification of /dev/sdb. (this step is rather irrelevant, but it's just for completeness).
Now, with all this in place, I update mdadm.conf:
=# mdadm --detail /dev/md0 --brief >> /etc/mdadm/mdadm.conf && update-initramfs -u
This added line:
ARRAY /dev/md0 metadata=1.2 name=debian:0 UUID=55692d54:b0beedae:9d85bc20:324d7f9f
With this in place, I reboot the system, to make sure it works ok. And immediately it crashes, on GRUB, with message:
error: disk `lvmid/F9eO8I-PB9F-Dsli-ZOSY-rVA1-7a37-Faos46/1N3Ah7-wIjT-HFxc-MS9U-lAcw-tYZw-N7sRO8' not found.
Entering rescue mode...
grub rescue>
ls in the prompt shows:
(hd0) (hd0,msdos1) (hd1) (hd1,msdos1) (hd2) (hd2,msdos2) (hs2,msdos1) (hd3) (hd3,msdos2) (hd3,msdos1)
What did I do wrong? What have I forgotten?
