This is a guide about adding a new disk to an existing [LVM](http://en.wikipedia.org/wiki/Logical_Volume_Manager_%28Linux%29 "Logical Volume Manager") VG
Check current setup
- First let’s check and document the current setup.
- Checking the /proc filesystem:
# cat /proc/partitions major minor #blocks name 8 0 7880544 sda 8 1 248832 sda1 8 2 1 sda2 8 5 7628800 sda5 252 0 6574080 dm-0 252 1 1036288 dm-1 - Using
lsblk:# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 7,5G 0 disk ├─sda1 8:1 0 243M 0 part /boot ├─sda2 8:2 0 1K 0 part └─sda5 8:5 0 7,3G 0 part ├─ubuntu--vg-root 252:0 0 6,3G 0 lvm / └─ubuntu--vg-swap_1 252:1 0 1012M 0 lvm [SWAP]
- Check and document the LVM layout.
- Volume Group info:
# vgs VG #PV #LV #SN Attr VSize VFree ubuntu-vg 1 2 0 wz--n- 7,27g 16,00m - Physical Volume info:
# pvs PV VG Fmt Attr PSize PFree /dev/sda5 ubuntu-vg lvm2 a-- 7,27g 16,00m - Logical Volume info:
# lvs LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert root ubuntu-vg -wi-ao---- 6,27g swap_1 ubuntu-vg -wi-ao---- 1012,00m
Add a new physical or virtual disk
Now add the new disk on your server. On VMs it is possible to add a new disk without powering off. On physical servers this can be possible too if the server comes with hot-swap functionality. Check your server specs first!
- Check if the new disk is detected.
- You can use this command if you want your system to detect the new disk without rebooting:
# for SCSI_HOST in /sys/class/scsi_host/* ; do echo "- - -" > $SCSI_HOST/scan ; doneThe above command simply loops through the SCSI hosts under the /sys/class/scsi_host directory and sends the "– – –" string to them. This forces the SCSI hosts to detect the new disk that has been attached.
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Using the /proc filesystem:
# cat /proc/partitions major minor #blocks name<br /> 8 0 7880544 sda 8 1 248832 sda1 8 2 1 sda2 8 5 7628800 sda5 8 16 31522680 sdb 252 0 6574080 dm-0 252 1 1036288 dm-1The size of the disk in GB, is 30GB:
# echo '31522680/1024/1024' | bc -l 30.06237030029296875000 - Using
lsblk:# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 7,5G 0 disk ├─sda1 8:1 0 243M 0 part /boot ├─sda2 8:2 0 1K 0 part └─sda5 8:5 0 7,3G 0 part ├─ubuntu--vg-root 252:0 0 6,3G 0 lvm / └─ubuntu--vg-swap_1 252:1 0 1012M 0 lvm [SWAP] sdb 8:16 0 30,1G 0 disk
Add the new disk to LVM Volume Group
- Create a new partition on the new disk:
# fdisk /dev/sdb Welcome to fdisk (util-linux 2.25.2). Changes will remain in memory only, until you decide to write them. Be careful before using the write command. Device does not contain a recognized partition table. Created a new DOS disklabel with disk identifier 0xaea3ab78. Command (m for help): n Partition type p primary (0 primary, 0 extended, 4 free) e extended (container for logical partitions) Select (default p):< Using default response p. Partition number (1-4, default 1): First sector (2048-63045359, default 2048): Last sector, +sectors or +size{K,M,G,T,P} (2048-63045359, default 63045359): Created a new partition 1 of type 'Linux' and of size 30,1 GiB. Command (m for help): t Selected partition 1 Hex code (type L to list all codes): <strong>8e Changed type of partition 'Linux' to 'Linux LVM'. Command (m for help): <strong>w</strong> The partition table has been altered. Calling ioctl() to re-read partition table. Syncing disks. - Verify the creation of a new partition:
# fdisk -l /dev/sdb Disk /dev/sdb: 30,1 GiB, 32279224320 bytes, 63045360 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: dos Disk identifier: 0xaea3ab78 Device Boot Start End Sectors Size Id Type /dev/sdb1 2048 63045359 63043312 30,1G 8e Linux LVM
Add the new partition to the Volume Group
- Extend the Volume Group by adding a new disk:
# vgextend ubuntu-vg /dev/sdb1 Physical volume "/dev/sdb1" successfully created Volume group "ubuntu-vg" successfully extended - Check the current free space of the Volume Group:
# vgs VG #PV #LV #SN Attr VSize VFree ubuntu-vg 2 2 0 wz--n- 37,33g 30,07g - Verify the new Physical Volume:
# pvs PV VG Fmt Attr PSize PFree /dev/sda5 ubuntu-vg lvm2 a-- 7,27g 16,00m /dev/sdb1 ubuntu-vg lvm2 a-- 30,06g 30,06g - Check the state of the Logical Volumes:
# lvs LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert root ubuntu-vg -wi-ao---- 6,27g swap_1 ubuntu-vg -wi-ao---- 1012,00mNothing changed yet, of course.
Resize the logical volume
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Use the
lvresizecommand to resize the root volume:# lvresize -L 30,07g /dev/ubuntu-vg/root Rounding size to boundary between physical extents: 30,07 GiB Size of logical volume ubuntu-vg/root changed from 6,27 GiB (1605 extents) to 30,07 GiB (7698 extents). Logical volume root successfully resized - Verify the volume resize:
# lvs LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert root ubuntu-vg -wi-ao---- 30,07g swap_1 ubuntu-vg -wi-ao---- 1012,00mThe root volume is now at 30,07GB. Good.
Resize the filesystem
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Check the current filesystem size:
# df -hT Filesystem Type Size Used Avail Use% Mounted on udev devtmpfs 485M 0 485M 0% /dev tmpfs tmpfs 100M 5,1M 95M 6% /run /dev/mapper/ubuntu--vg-root ext4 <strong>6,1G</strong> 2,4G 3,4G 41% / tmpfs tmpfs 496M 0 496M 0% /dev/shm tmpfs tmpfs 5,0M 4,0K 5,0M 1% /run/lock tmpfs tmpfs 496M 0 496M 0% /sys/fs/cgroup /dev/sda1 ext2 236M 40M 184M 18% /boot tmpfs tmpfs 100M 16K 100M 1% /run/user/1000Still using the old size, as expected.
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Resize the root filesystem:
# resize2fs /dev/mapper/ubuntu--vg-root resize2fs 1.42.12 (29-Aug-2014) Filesystem at /dev/mapper/ubuntu--vg-root is mounted on /; on-line resizing required old_desc_blocks = 1, new_desc_blocks = 2 The filesystem on /dev/mapper/ubuntu--vg-root is now 7882752 (4k) blocks long. - Verify the new size of the root filesystem:
# df -hT Filesystem Type Size Used Avail Use% Mounted on udev devtmpfs 485M 0 485M 0% /dev tmpfs tmpfs 100M 5,1M 95M 6% /run /dev/mapper/ubuntu--vg-root ext4 30G 2,4G 26G 9% / tmpfs tmpfs 496M 0 496M 0% /dev/shm tmpfs tmpfs 5,0M 4,0K 5,0M 1% /run/lock tmpfs tmpfs 496M 0 496M 0% /sys/fs/cgroup /dev/sda1 ext2 236M 40M 184M 18% /boot tmpfs tmpfs 100M 16K 100M 1% /run/user/1000
So now we have a logical root volume that expands across multiple physical disks. Notice, however, that this is not a very solid setup, since the loss of one of the physical volumes can bring down the whole system along with your data. Thus make sure that you have a solid and tested backup procedure in place. The restore procedure should also be documented in every detail in your disaster recovery practices.
References
- http://tldp.org/HOWTO/LVM-HOWTO/index.html
- http://wingloon.com/2013/05/07/how-to-detect-a-new-hard-disk-without-rebooting-vmware-linux-guest/
2 replies on “Adding a new disk in an existing Volume Group (LVM)”
Excellent
Thank you
Excellent guide, thank you so much!