How long the DB server should be in hot backup state?

[krasimir_2]

Hi.
I have Informix, DP 5.5 and EVA5000. I want to implement ZDB and IR. I will use ZDB on raw disk (Informix DB). Informix will be in hot backup. I will use “onmode –c block” to start hot backup state and “onmode –c unblock” to stop hot backup.
I have question.
How long the Informix should be in hot backup state - for the whole period of creation of the snapclone or only for the time of snapclone starting up

[TTr · Accepted solution]

The snapclone makes a full copy of a LUN (or LUNs) so for a full point in time database state capture, the database must be in hot backup state.
In other words for as long as the raw informix disks are being read to make the clone, the database must be in hot backup state.

The snapclone is a full copy of your LUNs and takes long time.

A snapshot, gets created much quicker and will minimize the amount the database has to be in hot backup mode.

[krasimir_2]

How long does EVA 5000 create 300GB snap clone?

[TTr]

> How long does EVA 5000 create 300GB snap clone?

It depends on many factors.
how many disks/trays the EVA has
how many disks are in use by the LUN(s)
if the the source disks and the destination disks are the same set of disks
other i/o traffic in the same LUNs at the same time
other i/o trafffic in the array overall
array caching
etc.

It can be anybody's guess, I would guess 30 minutes.

[Uwe Zessin]

But a SnapClone works very similar to a SnapShot, so you should be fine to:

- put DB in backup mode
- start the SnapClone
- take the DB out of backup mode

Any changes to the original volume will be take care of by the SnapClone similar to the SnapShot - except that it will additionally make a full copy. The downside, of course, is that the SnapClone will put an additional I/O burden on the source disks, because it is reading ALL blocks.

I've once read that a SnapClone can be as fast as about 100 GigaBytes per hour. Of course this depends on the total load of th EVA, because the copy I/O is competing with the normal 'user' I/O.

[krasimir_2]

I will not create and manage manually replica. I will use ZDB. The SMI-S agent will create and manage replica. In hot-backup Informix work in read-only mode. Informix should be stay in read-only mode 2 minutes. I will fill onmode -c block in Stop / quiesce the application. See attachment.This command will start hot-backup (read-only mode). I will fill onmode -c unblock in Restart the application. This command will stop hot-backup (normal mode). I will use snap clone because I want to use IR. The informix data base is 300 GB. And QUESTION.
How long the Informix should be in hot backup state - for the whole period of creation of the snap clone (more than 2 minutes) or only for the time of snap clone starting up (smaller than 2 minutes)?

[TTr]

The nature of the snapclone is that it starts up as a snapshot so that it preserves the state of the source LUNs when the snapclone starts and allows the LUNs to be modified normally by the server/DB. So you are correct, you do not need to keep the database in hotbackup mode all the time.

Take a look at this document, it is for oracle but the idea is the same.

http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00386935/c00386935.pdf

As always, after you set this up, you need to test your method and recover informix in a test environemnt from the snapclone.