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
Steps:
 
 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 http://serverfault.com/questions/66638/how-to-extend-a-san-based-vdisk-in-red-hat-without-rebooting as follows:
 or refer to http://www.datadisk.co.uk/html_docs/redhat/rh_multipathing.htm  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 http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/pdf/DM_Multipath/Red_Hat_Enterprise_Linux-6-DM_Multipath-en-US.pdf page 21 – Resizing an Online Multipath Device
 multipathd -k
 resize map multipath-map-name # this might be optional too, according to
 http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&taskId=120&prodSeriesId=3559651&prodTypeId=18964&objectID=c02000699
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.
References:
 1. Moving root File Systems from a Single Path Device to a Multipath Device – http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/pdf/DM_Multipath/Red_Hat_Enterprise_Linux-6-DM_Multipath-en-US.pdf page 32.
 2. Moving swap File Systems from a Single Path Device to a Multipath Device
 http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/pdf/DM_Multipath/Red_Hat_Enterprise_Linux-6-DM_Multipath-en-US.pdf 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
 3600143800648a76c0000b001566f0888
verify fiber channel adapter port wwn matches between server and storage
[root@db01 zabbix]# more /sys/class/fc_host/host0/node_name 
 0x20000000c9928eb1
 [root@db01 zabbix]# more /sys/class/fc_host/host1/node_name 
 0x20000000c9928eb2
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
 or
 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
 pvdisplay
 pvresize /dev/sda1 or pvresize /dev/sda # grow pv
 vgdisplay
 lvextend
 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
 partprobe
 pvcreate /dev/sda2
 vgextend, lvextend, resize2fs etc
 
 7. References:
 a. Vmware Linux Guest Add a New Hard Disk Without Rebooting Guest – http://www.cyberciti.biz/tips/vmware-add-a-new-hard-disk-without-rebooting-guest.html
b. Multi-path Device Mapper for Linux Software – How to Resize an EVA LUN on RedHat 4.8 and Later –
 http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&taskId=120&prodSeriesId=3559651&prodTypeId=18964&objectID=c02000699
c. HP business support center – http://www.hp.com/bizsupport/
 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

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