ASM and Powerpath

[Popy]

Hi,

I am building a server which will eventually a single node RAC with ASM disks. No MCSG.

I have 4 SAN paths to each EMC LUN, so 4 device files for each LUN.

How can I ensure ASM is using all 4 paths ? Will ASM support multipathing with the help of Powerpath, if yes how to configure this ?

Expecting your valuable responses.

thanks,
Vijay

[John Guster]

you make an alias for each LUN, then present this alias to ASM.

[Popy]

John,

Thanks for the quick reply.

I am affraid I did not get what exactly u meant by alias.

I know I can create a command alias, how do you this this aliasing technology will work for this scenario.

Here how I will create a disk for ASM,

mksf -C disk -H -I /dev/dsk/

please help.

Thanks,
Vijay

[Popy]

can any ASM champ advise me on this please.

Vijay

[Oviwan]

Hey

Which version of hpux have you? on 11.31 it makes the dev files automatically.

Regards

[Oviwan]

Hey again

This could be a useful doc:
http://www.oracle.com/technology/products/database/asm/pdf/asm-on-emc-5_3.pdf

Regards

[Popy]

its hpux 11.23

[Yogeeraj_1]

hi,

I would simply prefer to isolate the ASM configuration with the DISK configuration.

The way to do it is:
(e.g.)
ln -s /dev/emcpowera /u02/oradata/asmdisks/disk01
ln -s /dev/emcpowerb /u02/oradata/asmdisks/disk02
ln -s /dev/emcpowerc /u02/oradata/asmdisks/disk03
ln -s /dev/emcpowerd /u02/oradata/asmdisks/disk04

Then when creating the disk groups for ASM, you can simply set the Disk Discovery Path to "/u02/oradata/asmdisks/disk*".

hope this helps!

Kind regards
yogeeraj

[Popy]

Yogeeraj,

That make sense, thank you. Did you try configuring this on your setup ? did u get a chance to actually experience a failover this way ( I mean the system behaviour when we loose one path to the LUN )

Vijayy

[Yogeeraj_1]

Hi Vijay,

Yes. since this is a fresh installation, i got to play a bit. Luckily we have 2 SAN switches and redundant paths. Upon switching off one of the SAN switches, the system continued to work without any glitches. Well, there was no load on the system. I didnt go upto breaking anything else yet :)

ASM is very powerful.

good luck and have fun before you go online.

kind regards
yogeeraj

[John Guster]

1. create an alias is on Linux platform.
2. in HP-UX 11.23 + EMC Powerpath: since there is no alias for each LUN, make sure you have redunduncy for each LUN: 2 switches, 2 HBA cards, powerpath failover option set right etc. take one of 4 paths to ASM, powerpath will take care of failover.