The process of data being copied from the meta to the BCV is something I can follow (run a symmir query command and watch the SyncInProg run), but the restore somehow is invisible (or simply not done using a "BCV restore").

I suspected the copy back from BCV to meta only to be needed when something goes wrong, because I couldn't see the copying back to the expanded meta taking place. So if I understand correctly, the BCV really is used and not just there for backup purposes ?

This is to be expected, there is an entry created in the GDAT table for the relationship that gets created between the original BCV and the STD, once the BCV is established to another device this will be cleared.

Paul,

the BCV that is used for protecting data, it needs to be the size of the meta being expanded, or the future capacity of the meta being expanded ?

Thanks

once the meta is expanded the BCV is released ?

No, the RAID level doesn't need to be identical.

So a 200GB RAID5 meta can be expanded using a 200GB 2-way-mir BCV. In fact: this is how we do it. We don't have RAID1 for production (I know, it's silly, but our customers are served by RAID5 only atm).

Simply expand the BCV then with the same number of ldevs as you expanded the original meta with ?

I have a pool of RAID1 storage just sitting there to be used for use in expansion changes. I configure it on a per case scenario with number of meta members and perhaps cylinder sizes etc etc

Yup. But if anyone asks for a meta expansion of more than a TB, I think we're running into probs after all. Growing from 200 to 300 is ok, but the larger they get, the more temporary BCV space I need

you're well covered then

The BCV being used for the expansion should match the original STD Meta, i.e. have the same meta count/number of cylinders etc. It is not available for future incremental establishes with the newly expanded meta.

Yes, BCV is released and can be used for another meta expansion, or for establish with another STD.

Message was edited by:
PaulCork

yeah..i've done windows expansions more times then i want to mention here . For *nix i prefer to create another hyper/meta and use LVM expansion. I have never had to do a striped meta expansion, concatenated as piece of cake. Unfortunately on my box everything is Raid-5 ..so i would not be able to expand a striped meta without losing data.

The next thing is of course to do an expand or equivalent on the host.
for Windows you do a rescan and you'll find out that the disk grew and the partition didn't. Use "diskpart" and select the right volume and type "expand" to have the partition expanded to the disk (lun) boundary.
On other OS's this might be different. Simply create a new partition or do a similar expand "trick".

A Summary.

A RAID5 BCV cannot be used for the expansion because it uses redirection technology (timefinder emulation) and the concepts behind the script require the moving mirror type of establish. Although a RAID5 BCV cannot be used a RAID5 STD can be expanded but you must use STANDARD-NON-RAID5 BCV device to be able to perform action.

The BCV needs to be the size of the meta before expansion (and it must match the exact size and the number of meta members)