Adding disks to a RAID logical volume

[John Sherman_1]

We have a RAID system that we are planning on adding additional capacity to (i.e. more drives) and I have questions about how to insure we can "see" the new capacity after changing the configuration of the RAID.

Our current system has a 67GB RAID volume configured as a single volume group and single logical volume. The data is arranged in a RAID 5 configuration (stripe w/ parity). I will be adding 33GB to the RAID and the RAID system can automatically take care of adding the drive and re-striping the data, etc.

My concern is how to modify the HP volume group and/or logical volume to take advantage of this new space.

Is it as simple as using lvextend and extendfs?? This works great when you extend a LV with disk space that already existed on the volume group. In my case, the volume group has actually changed in size.

Any help is greatly appreciated. I am running on a K460 with HPUX 11.00. The RAID system is an LSI E2400 (aka StorageTek D173).

Thank you,
John Sherman

[Marco Santerre]

Though I do not know how an LSI E2400 works, chances are, what will happen, is that you'll have a whole new bunch of disk devices that will be installed on your system.

In order to recognize them, you'll have to do
#ioscan -fnC disk
#insf -e
to create the disk device files for those new disks.

Take note, of the new disks that you just installed, then
#vgextend vgname /dev/dsk/newdisks

After that you can do the lvextend command
#lvextend -L 100000 /dev/vgname/lvname

and if you have Online JFS, you just have to use the fsadm command to extend the file system, otherwise, you'll have to unmount the file system and then do the extendfs command.

[Bill McNAMARA_1]

as Marco mentions, your logical volumes on which you build your filesystems are based on LVM and are typically blind to the fact that there is a hardware raid system underlying them. The hardware raid system you are using need to incorporate the addidional disk in the LUN (raid volume). This LUN is seen as your physical volume, now with lvm there is no pvextend command, so you're going to find yourself in trouble because of this - ie you need to pvcreate again... so the answer is no, you can't.

Later,
Bill

[Leif Halvarsson_2]

Hi,
Is it possible, with the LSI E2400 to assign the new disk capacity to a new LUN. In this case this LUN can be added to the volumegroup as a new disk.

[Bill McNAMARA_1]

So with this array do you get a disk device file for every single disk or a single disk device file per lun?

If per disk then Leif is correct.

[John Sherman_1]

Thank you for the responses. The feedback from the RAID vendor is that I can increase the size of the LUN in the RAID system and then I can simply use lvextend and extendfs to increase the size.

This sounds great but I recall reading that you cannot increase the size of a LUN. Therefore, I am a little skeptical of counting on this.


Any thoughts?
John Sherman

[Marco Santerre · Accepted solution]

If your vendor is right by saying that you can increase the size of the LUN, unfortunetaly you won't be able to use the new extents of that LUN as your Volume Group has set a maximum number of extent per disk at its creation. Therefore, your disk can only grow as big as that number and all other extents will be lost unless you re-create your Volume Group.