Migrating old storage to new storae

[KPS]

Scenario we're dealing with here is that we're moving from one DMX to a newer one.
We intended to use pvmove initially, but instead would prefer to use LVM Mirroring. The new DMX lun sizes will be much larger than the ones we're using now on the old DMX.
We currently have luns setup so they are are dedicated to an lvol/filesystem and not spanning multiple filesystems in a given VG.

Question: If we have a lvol with say 3 luns in it at 100GB each, can we mirror that to a new lun that is at a size of 300GB?
Will LVM complain about this or is the minimum requirement that the target lun you're mirroring to has to be equal or larger than the source as far as PE's go?

If someone could confirm this for us we would really appreciate it.

Thanks
/KPS

[Shibin_2 · Accepted solution]

I assume that you are not using any PVG-strict/distributed policy in your lvol.

If no such allocation policy, you can mirror it.

When you do mirroring, your target LUN must have equal or larger size.

[James R. Ferguson]

Hi KPS:

LVM mirroring occurs at the logical volume level. The underlying LUN size doesn't matter as long as there are enough logical extents to complete the mirror.

> Shibin: I assume that you are not using any PVG-strict/distributed policy in your lvol.

You can use 'lvchange' to turn off the distributed allocation policy if you currently have that policy in force. The 'lvchange' can also set a simple strict allocation instead of a PVG one if necessary. See the manpages for more information.

Regards!

...JRF...

[KPS]

Thanks for confirming this for us. We do not have any PVG/Strict policies in place so sounds like we'll be imbibed from any issues there. The only other limitation we'll be looking at is our "Max PV's in pour VG config as our's is set to 144.

Thanks again PTA assigned......

KPS

[Bill Costigan]

One other issue you might run into is the max extents per PV. If the oringal LUNs were 100GBs then perhaps the max size of a PV based on the MAX Extents per PV and extent size might be 100GB.