Extend SAN disk under Linux LVM

Posted by Parthiban Ponnusamy

In Linux server, How to extend the SAN disk under LVM , after the LUN expanded from SAN? 

This article will explain you, how to do this. we are going to expand size of the SAN disk which is 20GB to 75GB under LVM. Basically, Linux detects the new size after a LUN scan, but LVM won't recognize expanded size of the disk. Let us see, how we are going to achieve this.

1. Scan for new LUNS. Refer Scan and Configure New LUNS for scanning LUNS in Linux

2. After scanning, check physical size of  the drive now.

# fdisk -l /dev/sdb
       
Disk /dev/sdb: 75.1 GB, 75161927680 bytes
255 heads, 63 sectors/track, 9137 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
 
Device Boot      Start         End      Blocks   Id  System

Now,  Linux recognized the new size as 75 GB.

3. Check the LVM

# pvs   
PV         VG      Fmt  Attr PSize  PFree
/dev/sda3  system  lvm2 a-   16.89G  2.92G
/dev/sdb   system2 lvm2 a-   20.00G 96.00M

 This command still reported 20GB for the LVM disk, Lets do a scan now:

# pvscan
# vgscan
# lvscan

# pvs   
PV         VG      Fmt  Attr PSize  PFree
/dev/sda3  system  lvm2 a-   16.89G  2.92G
/dev/sdb   system2 lvm2 a-   20.00G 96.00M

4. After the scan also, LVM still reports the disk as 20GB. So let us extend the size manually.
       

#  pvresize --setphysicalvolumesize 70G /dev/sdb
#  pvs

PV            VG      Fmt  Attr PSize  PFree
/dev/sda3  system  lvm2 a-   16.89G  2.92G
/dev/sdb   system2 lvm2 a-   70.00G 96.00M

Now LVM reports the new size of the disk.  Let us do a scan again, so that VG takes this new PV size into account.

# pvscan
# vgscan
# lvscan

5. Now, we can extend the logical volume size:

#  lvextend -L +50G /dev/system2/app
#  resize_reiserfs /dev/system2/app

# pvs
# vgs
VG      #PV #LV #SN Attr   VSize  VFree
system    1   5   0 wz--n- 16.89G  2.92G
system2   1   1   0 wz--n- 70.00G 96.00M

# lvs
LV   VG      Attr   LSize  Origin Snap%  Move Log Copy%
Opt  system  -wi-ao  2.00G
root system  -wi-ao  1.00G
tmp  system  -wi-ao  2.00G
usr  system  -wi-ao  2.97G
var  system  -wi-ao  6.00G
app  system2 -wi-a- 69.90G
       
6. Finally verify the space

# df -h  /app
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/system2-app
                           70G  5.5G   65G   8% /app
Thats all..! we are done..enjoy..

For Further Reading,
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I'm Parthiban, An UNIX System Admin by Profession. I'm Experienced in Linux/Unix System Administration and Scripting. I have done lot of work on the infrastructure Mgmt side in Linux, UNIX and Windows system administration, Hardware, Storage and Data center. I'm blogging since 2008.
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