Re: ASM and EMC PowerPath

  • From: Karl Arao <karlarao@xxxxxxxxx>
  • To: "Radoulov, Dimitre" <cichomitiko@xxxxxxxxx>
  • Date: Mon, 11 Apr 2011 04:30:52 +0800

Hi Dimitre,

See my answers below..

1) but in order to actually use the multipath, you need to configure it
correctly (check MOS Note 394956.1).

ANSWER: Also see the following notes
- Configuring Oracle ASMLib on Multipath Disks [ID 309815.1]
"Unlike most multipath drivers, PowerPath will support full multipath
capabilites even with the regular names. PowerPath and ASMLib now work
together successfully."
- ORA-15072 when creating a diskgroup with external redundancy [ID 396015.1]
which pertains to the "Linux multipath" and not the "EMC Powerpath"


2) if on reboot (or after scandisk) asmlib chooses a path different than the
multipath
and the chosen path becomes unavailable, you won't be able to access those
disks
no more (you'll get errors)

ANSWER:
- it will not choose a path other than the configured EMC Powerdevice if you
have properly configured the persistent binding... so you must ensure that
the storage engineer have properly configured the "multipathing" and
"persistent binding"


3) If you configure the access to the disks with asmlib (via scanorder or
scanexclude)
through the multipath, the disks will remain accessesible even if you loose
one or more
of the paths to those disks (assuming at least one path is still available).

ANSWER:
- again.. "Unlike most multipath drivers, PowerPath will support full
multipath capabilites even with the regular names. PowerPath and ASMLib now
work together successfully."



The only error so far that I've seen on EMC multipathing is this.. which you
can ignore as per powerlink
http://karlarao.tiddlyspot.com/#[[Buffer%20IO%20error]]
and the only time I have to exclude powerdevices is when I have to configure
it for LVM ... http://karlarao.tiddlyspot.com/#EMCPowerDevicesOnLVM


-- 
Karl Arao
karlarao.wordpress.com
karlarao.tiddlyspot.com

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