Re: ASM switching storage

From: Martin Klier <>
Date: Thu, 18 Dec 2008 14:13:25 +0100
Message-ID: <>

Hi Luka,

Luka Grah schrieb:
> I have one question about switching external storage for Oracle RDBMS.
> Oracle uses ASM and disk devices are masked using symbolic links.
> We want to change storage - we bought a new storage arry .
> For moving Oracle I was considering two options for ASM data migration:
> - Using ASM, add new disks and drop the old one and let ASM rebalance data.
> - To copy data using storage tools and then just change symbolic links
> locations.
> Would the second method work?

Maybe, but I'd prefer the first one: No matter what kind of redundancy (NORMAL, EXTERNAL ...) you are using, adding and removing disks from the disk group works simultanously, as long as you are starting it within one command. ASM_POWER_LIMIT or the command itself allows you to configure the number of processes used for the operation, in a range between 1 and 11 (don't ask why), Oracle recommends to use it about 7.

This way is usable, as long as you can run the drivers for your old and your new storage can be run at the same time on the same machine.

Another nice aspect: The more DB write operations you are are performing in this time, the faster the rebalancing works: Every write will be performed on the new disks.

Of course, if you are doing all this on RAC, make sure the (raw-)devices of the new LUNs are the same on all hosts again.

Martin Klier

Usn's IT Blog for Linux, Oracle, Asterisk

Received on Thu Dec 18 2008 - 07:13:25 CST

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