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Re: [Linux-cluster] Multipath or Oracle RAC ASM issue?



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Joel Becker wrote:
> On Thu, Jun 19, 2008 at 12:43:55AM +0100, Bryn M. Reeves wrote:
>> It is important here to make sure that the aliases are synchronised. You
>> can do this by syncing the bindings file between the hosts or by using
>> explicit alias { /*...*/ } entries in multipath.conf.
> 
> 	I assume you're talking about synchronizing the mpathX aliases.
> the LANDx names were selected by the user via ASMLib, and not part of
> the usual multipathd/udev/dm stuff.

Yes - just the multipath aliases, either in the bindings file or
multipath.conf. This applies any time you want to have mpath0 or
whatever be the same device across a set of machines that all see the
same storage. If ASM uses labels then it might not actually matter that
the aliases differ across nodes but administrators find it less confusing.

> 	I wish they would leave the /dev/dm-N nodes alone.
> /dev/mapper/* doesn't show up in /proc/partitions, and thus is
> impossible to scan simply for.  A future ASMLib toolset will have new
> scan code that walks /sys/block and can handle devices that don't show
> up in /proc/partitions, but current releases need /dev/dm-X nodes.  When
> people run into that, I have them uncomment that rule in udev.

Hmm, interesting - hadn't considered this case. Most of the tools that I
work with do use /sys/block for scanning purposes but I do know of code
out there that does rely on the content of partitions and you're right
of course that this won't work if the /dev/dm-N entries aren't there.

Regards,
Bryn.

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