How to add LUN disk online under CentOS 6.2

Jephe Wu -

Environment: CentOS 6.2 64bit with multipath connected to HP EVA storage, the LUN disk was LVM disk
Objective: add a new LUN disk for server online and add into the existing LVM to make the partition size bigger
scenario: LVM add new lun disk, increase the existing lvm lun disk, increase the existing partition disk such as /dev/sda1


1. add a new LUN disk in EVA storage and present it properly to the server
2. use commands below to rescan scsi hosts

 echo "- - -" > /sys/class/scsi_host/host0/scan   
 echo "- - -" > /sys/class/scsi_host/host1/scan 
 echo "- - -" > /sys/class/scsi_host/host2/scan 

you can find out how many scsi disks you have by running "ls /sys/class/scsi_host", or just run above commands for all hosts under /sys/class/scsi_host

2.1 if you increased the existing LUN disk size, please refer to as follows:
or refer to  Resize online multpath LUN part  and Multipathing and DR part

resize SAN disk / physical device first.

# rescan disk size
multipath -ll # list all disks, for all disk, run
echo 1 > /sys/block/sdX/device/rescan
#run for all sdX under /sys/block

[#optional, then you can test multipath failover by running]
multipathd -k
del path sdx 
add path sdx

# resize mapname
note: refer to page 21 - Resizing an Online Multipath Device
multipathd -k
resize map multipath-map-name # this might be optional too, according to

multipath # run this command to make multipath pickup the new size according to above hp bizsupport

use multipath -ll to verify the new size, then
pvresize,lvextend and resize2fs to expand the disk to new size.

1. Moving root File Systems from a Single Path Device to a Multipath Device - page 32.
2. Moving swap File Systems from a Single Path Device to a Multipath Device page 34

3. verify wwid for new lun disk ndb01-b  - optonal
[root@db01 sys]# multipath -ll
mpatha (3600508b1001030363946364434300999) dm-0 HP,LOGICAL VOLUME
size=137G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  `- 2:0:0:0 sda 8:0    active ready running
ndb01 (3600143800648a76c0000b00037b10777) dm-5 HP,HSV300
size=200G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 1:0:0:2 sdc 8:32   active ready running
  |- 1:0:1:2 sdf 8:80   active ready running
  |- 0:0:0:2 sdi 8:128  active ready running
  `- 0:0:1:2 sdl 8:176  active ready running
ndb01-b (3600143800648a76c0000b001566f0888) dm-11 HP,HSV300
size=200G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 0:0:0:4 sdn 8:208  active ready running
  |- 0:0:1:4 sdq 65:0   active ready running
  |- 1:0:0:4 sdt 65:48  active ready running
  `- 1:0:1:4 sdw 65:96  active ready running\

you can get a lun disk wwid by running:
/lib/udev/scsi_id --page=0x83 --whitelisted --device=/dev/sdw

verify fiber channel adapter port wwn matches between server and storage 

[root@db01 zabbix]# more /sys/class/fc_host/host0/node_name 
[root@db01 zabbix]# more /sys/class/fc_host/host1/node_name 

then check EVA storage Hosts - port tab part to confirm

4. modify /etc/multipath.conf to add new wwid for new LUN disk
vi /etc/multipath.conf
multipaths {
        multipath {
                wwid 3600143800648a76c0000b00037b50005
                alias db01
        multipath {
                wwid 3600143800648a76c0000b001566f0888
                alias db01-b

fdisk -l | grep sd # check the last disk detected by os
ls /dev/mapper -l # check the existing lun disks
chkconfig multipathd on
/etc/init.d/multipathd start # make sur start it
/etc/init.d/multipathd reload
go to /dev/mapper to run ls -l to verify newly add LUN disks
fdisk -l | grep sd #confirm new disks have been detected.

5. resize pv and file system
pvcreate /dev/mapper/ndb01-b
pvresize /dev/mapper/ndb01 # if you increase the existing lun disk

vgextend VgGroup1 /dev/mapper/ndb01-b
lvextend -L +150G /dev/VolGroup01/ndb01-mysql1
resize2fs /dev/VolGroup01/ndb01-mysql1
df -h

6. what if it's a single lun disk in OS - /dev/sda
lun admin to resize disk
echo "- - -" > /sys/block/sda/device/rescan
fdisk /dev/sda #remove then readd a partition that is the new disk size
partprobe # to update /proc/partitions
pvresize /dev/sda1 or pvresize /dev/sda # grow pv
e2fsck -fy /dev/VolGroup1/LogVol1 # optional
resize2fs /dev/VolGroup1/LogVol1

or, instead of growing pv, you can use the new added partiton size to create another pv
fdisk /dev/sda # to add a new partition, not to delete/create
pvcreate /dev/sda2
vgextend, lvextend, resize2fs etc

7. References:
a. Vmware Linux Guest Add a New Hard Disk Without Rebooting Guest -

b. Multi-path Device Mapper for Linux Software - How to Resize an EVA LUN on RedHat 4.8 and Later -

c. HP business support center -
d. search redhat customer portal for article - How to extend filesystem built on LVM SAN disks on RHEL5
e. HP EVA storage default port 2372 with https