Can I grow a LUN & the volume in it?

[kail su]

Pardon me if this is a dumb question.

Some of the systems that we have today have 8G LUNs. I want to grow the LUNs within the array and make it 16G each (The array that we have today allows us to do this). Will LVM on the host recognize this? If yes, what do I need to do?

I was thinking that the following might work: I will do pvchange -x y to allow the extends to grow and then when I increase the size of the LUN, I can come back to the host and do a lvextend. Will this work?

Thanks
Kail

[Steven E. Protter]

It depends on what kind of array you have. I believe some HP disk arrays will recognize the space.

With the non-HP arrays that we use, we've had to back up the logical volumes on the LUN and start over with lvcreate.

If your system is going to recognize the increased space without a destructive process, these are the steps.

After the expansion of the lun,

try ioscan

then

ioscan -fnC disk

see if the size is bigger.

Maybe try SAM disks disk devices and check the size. If it shows up bigger, lvextend and extendfs will work. If not, keep trying.

Boot your box and repeat the above steps.

If the space is not recognized, back up the data prior to a maintenance window.

SEP

[Patrick Wallek]

I doubt that LVM would deal well with increasing LUN sizes. It MIGHT work.

I would be more comfortable just creating a new LUN, assigning it to the machine, doing an 'insf -e' to create the device files for it and then extending the VG and the LV with the additional space.

[Sanjay_6]

Hi,

I'm not sure you ca ndo that. You may have to take a backup of all the data on the lun and then recreate the VG/lv info in the disk after the lun size is increased.

Take care that the max PE for the vg is more that the size of the new lun.

Hope this helps.

Regds
Sanjay

[Uday_S_Ankolekar · Accepted solution]

You can not the modify the size of the existing LUN , Create new LUN with desired size and move data on this new LUN and then delete old LUN if everything working well.

Goodluck,
-USA..

[F Verschuren]

Even if it is poseble to extend a lun it is not always poseble to put that bigger lun in the volumegroup because if You look whit vgdisplay to the following parameters:
Max PE per PV 2500
PE Size (Mbytes) 4
If you put in a bigger disk you are not abel to alocate more than the [Max PE per PV] * [PE Size]

[RolandH]

Hi Kail Su,

first of all this is your first question in the forum - right! WELCOME to our community!!!

To your question.

Do it like patrick said it the smartest way.
The LVM treats a LUN like a physikal device.
So the easiest way for your is to create a new LUN with the same specifications as your original LUN. Then map it to your system and do an "ioscan -fnCdisk". All your disk will be listed with its device files ( /dev/dsk/cXtYdZ ) but there is one disk without device files. This is your new disk. Note the hardware path of that device and create the device files "insf -H "
now figure out the device files of your new disk "ioscan -fnH".

Now you can create a LVM disk and add this disk to your volume group you want increase.

# pvcreate /dev/rdsk/cXtYdZ
# vgextend vg## /dev/dsk/cXtYdZ

Now your volume group has double size (vgdisplay vg##) and you can extend your lvol to double size.

HTH
Roland

[Alzhy]

I've used to date arrays from HP (XP series, HSG, AutoRAID), Sun (RM, 3500, 9900) and Amdahl -- none of these I think support on-line LUN expansion due to the nature of their RAID configurations.

What I usually do is on VxVM (dunno if there is an equiv on LVM) is to use vxevac - to evactuate volume components (subdisks or lvols) on the LUN, expand the LUN and copy back those objects... All these can be done on-line without impacting the applications... On emore reason why VxVM is superior to most LVM's...