Adding a new disk to an existing LVM Volume

In a previous post, I described how to build an LVM based NAS using Ubuntu.

Now I've reached the stage where that NAS is full so I want to add a new drive. The existing Volume Group consisted of 2 x 2TB hard drives and I'm adding a third.

The system is Ubuntu 13.04 "raring" but the following should work equally well on any Debian (or indeed Redhat) based system.

Here is what I did.

The first and most important step is to backup all the data on your drive! When we play around with disks and partitioning we can destroy terabytes of data with just one mistake. I used a 4TB external USB drive. You have been warned. OK, second thing I did naturally, was install the new drive, which in my case also required installing a new SATA interface in the server, which went surprisingly smoothly.

OK, with all the preliminaries in place, we can proceed to making use of the new hard drive.

I used fdisk -l to determine that my new drive was detected by the system and that it is device /dev/sdf.

I used parted to partition it.

Also using parted, I set the LVM flag:  

set 1 lvm on

Back to the bash console, I added the drive as a new physical volume:  

# pvcreate /dev/sdf1

Confirm that this went OK.

 # pvdisplay 
  --- Physical volume ---
  PV Name               /dev/sdc1
  VG Name               store
  PV Size               1.82 TiB / not usable 4.09 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              476931
  Free PE               0
  Allocated PE          476931
  PV UUID               2dvFBg-uAFn-kudl-JW14-UkgE-EvPq-G5Ye5Q
  
  --- Physical volume ---
  PV Name               /dev/sde1
  VG Name               store
  PV Size               1.82 TiB / not usable 4.09 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              476931
  Free PE               0
  Allocated PE          476931
  PV UUID               BH8Osp-7UR7-6YVh-sbVe-zvCh-6WC9-hQkozl

 "/dev/sdf1" is a new physical volume of "1.82 TiB"
 --- NEW Physical volume ---
  PV Name               /dev/sdf1
  VG Name     
  PV Size               1.82 TiB          
  Allocatable           NO 
  PE Size               0 
  Total PE              0
  Free PE               0 
  Allocated PE          0 
  PV UUID               29ZZUV-qg34-Vcm9-Gw4M-iGau-eTiD-E0geXp

My VG (Volume Group) is named store, you can determine this with the vgdisplay command:  

# vgdisplay --- Volume group --- VG Name store 
 [...] 
 VG Size 3.64 TiB 
 [...]

Note: I have cut out the info that we are not interested in from this output, as indicated by [...]

Now, extend the VG "store" onto my new drive:  

# vgextend store /dev/sdf1

Check the VG again to find that my VG has grown to 5.46T:

# vgdisplay
 --- Volume group --- 
 VG Name              store
 [...]
 VG Size              5.46 TiB 
 [...] 
 Alloc PE / Size      953862 / 3.64 TiB 
 Free  PE / Size      476931 / 1.82 TiB 
 [...]

I want to use all the space for my existing LV (logical volume), so I must extend it with the lvextend command.

Before we do that, let's have a look at the existing LV details:  

# lvdisplay 
  --- Logical volume --- 
  LV Path                /dev/store/library
  LV Name                library
  VG Name                store
  LV UUID                Jo8uag-AkXk-8p7s-4x01-IFS9-FuWz-3MMSQH
  LV Write Access        read/write
  LV Creation host, time jupiter, 2013-05-17 17:25:01 +1000
  LV Status              available
  # open                 1
  LV Size                3.64 TiB 
  Current LE             953862 
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           252:0

I can see from that output that my LV is named "library". From the output of the above two commands we can assemble a command to extend the LV.  Note that from the earlier vgdisplay command we got this information:  

Alloc PE / Size 953862 / 3.64 TiB 
Free  PE / Size 476931 / 1.82 TiB 

If we take those two numbers and add them together (953862 + 476931) we can get the total number of "extents" in the volume group (1430793) and we can use that to extend the LV to take up all the free space:

 # lvextend -l1430793 /dev/store/library 
   Extending logical volume library to 5.46 TiB 
   Logical volume library successfully resized 

In the comments, Andrew suggests an easier way to allocate all the free space: 

# lvextend -l +100%FREE /dev/store/library

Check that everything is OK:

# lvdisplay
 --- Logical volume ---
  LV Path                /dev/store/library
  LV Name                library
  VG Name                store
  LV UUID                Jo8uag-AkXk-8p7s-4x01-IFS9-FuWz-3MMSQH
  LV Write Access        read/write
  LV Creation host, time jupiter, 2013-05-17 17:25:01 +1000
  LV Status              available
  # open                 1
  LV Size                5.46 TiB
  Current LE             1430793
  Segments               3
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           252:0

Everything looks OK so we proceed to the final part, which is to resize the actual file system. This is also the most dangerous part. You did make a backup right?

Before we can resize the file system, you will need to umount it;

# umount /dev/mapper/store-library

Just to be safe, make sure there are no file system errors:  

# e2fsck -f /dev/mapper/store-library

Finally, resize the file system:  

# resize2fs -p /dev/mapper/store-library

Now, the last two commands may take some time to complete, but once they are done (and assuming there were no problems of course) we can remount our LV and check out all that lovely new free space.

# df -h 
Filesystem                 Size  Used Avail Use% Mounted on
[..]
/dev/mapper/store-library  5.4T  3.6T  1.8T  67% /store/library

yay!