Using Oracle ASM with LVM

[Ben Dehner]

There was a recent thread posted about ASM at http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=1112061, which prompts a question.

Oracle ASM wants to be handed a disk/LUN like "/dev/dsk/cXtYdZ". However, ASM apparently does not respect multipathing, which is common in most SAN environments. Is it possible -- and supportable -- to use LVM to create a volume group containing the LUN and its alternate links, create an lvol, then give ASM the lvol device? Let pvlinks do its work, and hand Oracle the "/dev/vgXX/lvol" volume to do whatever it does.

We are not currently using 10g or ASM. I am looking into 10g, but we do not have any apps that require it, and it looks like it just isn't mature or stable enough yet to go there. And if ASM doesn't support multipathing, that puts that "feature" in the bit bucket right there.

[Yogeeraj_1 · Accepted solution]

Hi Ben,

there should not be any problem using ASM.

There is a recent white paper on Metalink which discusses Oracle ASM and Multi-pathing technologies.

See metalink Note: 294869.1
Subject: Oracle ASM and Multi-Pathing Technologies
Last Revision Date: 13-FEB-2007

It also discusses about the different OSes like HP-UX, AIX, LINUX, Tru64.

hope this helps!

kind regards
yogeeraj

[Yogeeraj_1]

hi again,

Please find below a simple quote from the above mentioned note:

This document will briefly discuss Multipath I/O and how Oracle Automatic Storage Management leverages multi-pathing.

An I/O path generally consists of an initiator port, fabric port, target port, and LUN. Each permutation of this I/O path is considered an independent path. Dynamic Multi-pathing/failover tools aggregate these independent paths into a single logical path. This path virtualization provides I/O load-balancing across the HBAs, as well as non-disruptive failover on HBA failures. Multi-pathing software requires all the required disks to be visible on each available and eligible HBA. These multi-paths will be detected by probing the World Wide Device Identifiers (WWD ID).

Multi-pathing software also provides multi-path software drivers. Most multi-pathing drivers are SCSA compliant pseudo nexus drivers, that support multipath services for fibre channel attached SCSI-3 devices. These drivers receive naming and transport services from one or more physical HBA devices. To support multi-pathing, a physical HBA driver must comply with the multi-pathing services provided by this driver.
...
Although ASM does not provide multi-pathing capabilities, ASM does leverage multi-pathing tools, as long the path or device produces a successful return code from an fstat system call.
...


This note also provides a list of MP utilities that are known working solutions.

hope this helps too!

kind regards
yogeeraj

[Ben Dehner]

Thank you. Apparently, Oracle does not formally support the various multipathing utilties, but they seem to work. To quote the article one last time,

"Oracle Corporation does not certify ASM against these multipathing utilities. The MP utilities listed below are ones that known working solutions".

Using LVM with the pvlinks functionality is not listed in their matrix of known working solutions, but it still might work.