LVM

Notes on LVM

1. PV commands => working on physical volume aka disk
2. VG commands => virtual groups
3. LV commands => logical volumes

Create

Create a bunch of small (100MB) virtual disks for use with LVM.

DISK_DIR=/var/tmp/disks
mkdir -p ${DISK_DIR} &&
for i in 1 2 3 4 5; do
    dd if=/dev/zero of=${DISK_DIR}/disk${i} bs=100M count=1 &&
    losetup /dev/loop${i} ${DISK_DIR}/disk${i} &&
    pvcreate /dev/loop${i}
done

Output should look like this

1+0 records in
1+0 records out
104857600 bytes (105 MB) copied, 0.50751 s, 207 MB/s
  Physical volume "/dev/loop1" successfully created
1+0 records in
1+0 records out
104857600 bytes (105 MB) copied, 1.94502 s, 53.9 MB/s
  Physical volume "/dev/loop2" successfully created
1+0 records in
1+0 records out
104857600 bytes (105 MB) copied, 4.12227 s, 25.4 MB/s
  Physical volume "/dev/loop3" successfully created
1+0 records in
1+0 records out
104857600 bytes (105 MB) copied, 1.51487 s, 69.2 MB/s
  Physical volume "/dev/loop4" successfully created
1+0 records in
1+0 records out
104857600 bytes (105 MB) copied, 3.88262 s, 27.0 MB/s
  Physical volume "/dev/loop5" successfully created

Confirm the output

# pvs
 PV         VG         Fmt  Attr PSize   PFree
 /dev/loop1            lvm2 --   100.00M 100.00M
 /dev/loop2            lvm2 --   100.00M 100.00M
 /dev/loop3            lvm2 --   100.00M 100.00M
 /dev/loop4            lvm2 --   100.00M 100.00M
 /dev/loop5            lvm2 --   100.00M 100.00M

Create Virtual Group

# vgcreate -s 1024K lpic /dev/loop[1-5]
 Volume group "lpic" successfully created
# pvs
 PV         VG         Fmt  Attr PSize  PFree
 /dev/loop1 lpic       lvm2 a-   99.00M 99.00M
 /dev/loop2 lpic       lvm2 a-   99.00M 99.00M
 /dev/loop3 lpic       lvm2 a-   99.00M 99.00M
 /dev/loop4 lpic       lvm2 a-   99.00M 99.00M
 /dev/loop5 lpic       lvm2 a-   99.00M 99.00M
 /dev/sda2  VolGroup00 lvm2 a-   37.12G     0
# vgs
 VG         #PV #LV #SN Attr   VSize   VFree
 lpic         5   0   0 wz--n- 495.00M 495.00M

Create Logical Volume

# lvcreate -n lv_lpic -L 256M lpic
 Logical volume "lv_lpic" created
# lvs
 LV         VG         Attr   LSize   Origin Snap%  Move Log Copy%  Convert
 lv_lpic    lpic       -wi-a- 256.00M

Manage

Move disk

Goal: move content of loop1 to loop5

#pvs
 PV         VG         Fmt  Attr PSize  PFree
 /dev/loop1 lpic       lvm2 a-   99.00M     0
 /dev/loop2 lpic       lvm2 a-   99.00M     0
 /dev/loop3 lpic       lvm2 a-   99.00M 41.00M
 /dev/loop4 lpic       lvm2 a-   99.00M 99.00M
 /dev/loop5 lpic       lvm2 a-   99.00M 99.00M
# pvmove /dev/loop1 /dev/loop5
 /dev/loop1: Moved: 100.0%
# pvs
 PV         VG         Fmt  Attr PSize  PFree
 /dev/loop1 lpic       lvm2 a-   99.00M 99.00M
 /dev/loop2 lpic       lvm2 a-   99.00M     0
 /dev/loop3 lpic       lvm2 a-   99.00M 41.00M
 /dev/loop4 lpic       lvm2 a-   99.00M 99.00M
 /dev/loop5 lpic       lvm2 a-   99.00M     0

Remove physical disk

Goal: remove /dev/loop4 from VG lpic

# pvs
 PV         VG         Fmt  Attr PSize  PFree
 /dev/loop1 lpic       lvm2 a-   99.00M 99.00M
 /dev/loop2 lpic       lvm2 a-   99.00M     0
 /dev/loop3 lpic       lvm2 a-   99.00M 41.00M
 /dev/loop4 lpic       lvm2 a-   99.00M 99.00M
 /dev/loop5 lpic       lvm2 a-   99.00M     0
# vgreduce lpic /dev/loop4
 Removed "/dev/loop4" from volume group "lpic"
# pvremove /dev/loop4
 Labels on physical volume "/dev/loop4" successfully wiped
# pvs
 PV         VG         Fmt  Attr PSize  PFree
 /dev/loop1 lpic       lvm2 a-   99.00M 99.00M
 /dev/loop2 lpic       lvm2 a-   99.00M     0
 /dev/loop3 lpic       lvm2 a-   99.00M 41.00M
 /dev/loop5 lpic       lvm2 a-   99.00M     0

Add physical disk

# pvs
 PV         VG         Fmt  Attr PSize  PFree
 /dev/loop1 lpic       lvm2 a-   99.00M 99.00M
 /dev/loop2 lpic       lvm2 a-   99.00M     0
 /dev/loop3 lpic       lvm2 a-   99.00M 41.00M
 /dev/loop5 lpic       lvm2 a-   99.00M     0
# pvcreate /dev/loop4
 Physical volume "/dev/loop4" successfully created
# pvs
 PV         VG         Fmt  Attr PSize   PFree
 /dev/loop1 lpic       lvm2 a-    99.00M  99.00M
 /dev/loop2 lpic       lvm2 a-    99.00M      0
 /dev/loop3 lpic       lvm2 a-    99.00M  41.00M
 /dev/loop4            lvm2 --   100.00M 100.00M
 /dev/loop5 lpic       lvm2 a-    99.00M      0
# vgextend lpic /dev/loop4
 Volume group "lpic" successfully extended
# pvs
 PV         VG         Fmt  Attr PSize  PFree
 /dev/loop1 lpic       lvm2 a-   99.00M 99.00M
 /dev/loop2 lpic       lvm2 a-   99.00M     0
 /dev/loop3 lpic       lvm2 a-   99.00M 41.00M
 /dev/loop4 lpic       lvm2 a-   99.00M 99.00M
 /dev/loop5 lpic       lvm2 a-   99.00M     0