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List:       aix-l
Subject:    Re: MPIO and Vpath
From:       Jonathan Fosburgh <syjef () MAIL ! MDANDERSON ! ORG>
Date:       2003-12-03 21:04:16
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On Wednesday 03 December 2003 11:37 am, Yi XIE wrote:
> Dear All,
>
>      When I use Shark, I always use Vpath.  But now I use AIX 5.2 which
> default use MPIO(but I can also use Vpath in AIX5.2).  But I found that
> MPIO hasn't takeover function which belongs to Vpath.  During the test,
> when I disconnect a fiber channel, the I/O cannot switch to another fiber
> channel.  Does anyone know if this sympton is true?  Thanks.
>

Well, first of all SDD and MPIO cannot coexist.  Second, MPIO for 2105
requires a special version of 2105.rte (available from storage.ibm.com) that
cannot coexist with the 2105.rte for SDD.  With those two points out of the
way, here are the issues as I am familiar with them.  Native MPIO is not as
flexible as SDD, the way it handles load-balancing is strictly round-robin,
but I think that SDD defaults (on AIX) to a different algorithm.  More
importantly, according to support, MPIO does not currently support concurrent
code loads on the Shark. That killed using MPIO for us.  I was looking at it
for my new systems until I found out about that.
- --
Jonathan Fosburgh
AIX and Storage Administrator
UT MD Anderson Cancer Center
Houston, TX
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