P4500 G2: Error creating snapshot. How much available space is required for a snapshot?

[Nick Salty]

HI There,

I have two HP P4xxx devices, one P4500G2 and P4300G2.  They are on separate sites, and I would like to create a remote snapshot of one of the volumes.

The remote copy schedule fails with the status of 'Failed'.

I can have traced the issue back to not being able to create a snapshot of the primary volume.

The error I receive is "Insufficient Space to Make The Requested Change".

I am trying to snapshot a volume that is fully provisioned and is 1.7TB, and there is 765GB available remaining in the cluster (of one).

I am able to create snapshots and remote snapshots of the other volumes, and new volumes on the same storage.

Can anyone help me work out what that error message really means?  Or, how much space I need to have available before being able to create a snapshot?

Thanks,

Nick

I am running SAN/iQ 9.0 on the P4500 and 9.5 on the P4300, but since I can create snapshots and remote copies of the other volumes, I doubt if this is the issue.

[oikjn]

you must convert the volume to "thin"  a full provusioned volume creates a full provisioned shapshot for some crazxy reason.  there is pretty much no reason not to use a thin provisioned LUN anyway, so just convert it to thiin and then you will be able to snapshot without issue.

I do suggest that its a good idea to create one full provisioned "empty" lun that is ~50-100GB in space depending on the size of your setup to use an an emergency reserve space in case you run out of space in your SAN you can always delete it to regain R/W control on the rest of your LUNs.

[Nick Salty]

HI Oikjn,

Thanks for taking the time to reply to me.

I n the intervening time between posting my question and receiving your reply, I logged a call with HP.  They told me that that is how it is, and that a snapshot requires the same space as the lun.

I did convert it to thin when working with HP support, but the issue remains.

Perhaps you could also help me understand the consumed space of a different volume?

The volume is 4.5TB, and had a snapshot of it which I have just deleted. 

The volume is network raid 10, but the consumed space is showing as 11.17TB.  That is more than double the volume total by quite a lot, so I don't understand where the extra 2.17TB is being used up!

Any advice gratefully appreciated.

[Nick Salty]

Just an update for all.

The snapshot took a few hours to clear (although there was no indication that anything was going on)

Many Thanks,

[oikjn]

yup, it takes a little while to reclaim the deleted snapshot space.