Snapshot & Cloning at HSG80 V8.7P

[Emad Omar]

Dear all,
I need to know if my existing Storage Array HSG80 V8.7P is supporting the snapshot and cloning or not? The existing devices are one storage array HSG80 V8.7P connected to the two Alpha Servers ES45(Cluster)running with OVMS V7.3-2 .I need to know if I can make a snapshot within this storage array and what is the suitable procedure to do that.Also I need to know how can I make an online backup from a snaphoted/cloned disks to a tape drive without causing interruption to the I/Os?? Is it possible to do that without causing an overhead to the whole systems.
Note that there is no backup software available and customer used to do a normal backup on a DLT tape drive.
Please advise . . .

Regards,
Emad Omar

P.S. This thread has been moved from General to Disk array. - Hp Forum moderator

[Uwe Zessin · Accepted solution]

ACS V8.7P does support snapshots and clones.

You have already asked about snapshots ;-)
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=835972

You say you have only one storage array, so you obviously don't use the replication feature in the "P" version - else, you need to keep in mind that snapshots are only supported at the target site.

Snapshots can be taken from any RAID level, but cloning is based on the split-mirror feature, so you CAN NOT clone RAID5-sets.

For a snapshot, you first create a temporary storageset that must be at least as large as the source unit and then proceed with the "ADD SNAPSHOT" command.

Please keep in mind that a snapshot or a split-mirror is not synchronized with the operating system. If you don't shutdown your application and dismount the disk before you take a 'point in time copy', the data on it will look like if the server has lost power - e.g. any host caches have not been flushed and the disk wasn't dismounted properly.

Of course, it is not possible to do that without 'overhead'.

For cloning, you need to do a full copy of your entire disk (=HSG unit) before you can do the split.

For snapshots, there is an ongoing 'copy-out' operation into the temporary storage set for any segment that is updated for the frst time by a host write. Don't forget that the snapshot shares all segments that have not been updated with the original disks, so your BACKUP will contend with the server I/Os.

You say that your customer is using OpenVMS, so he can continue to use the BACKUP command.