Last I heard, mixing multipath dasd with tape activity on the same FC card
is not supported, and from what I've seen on my system, this seems to be
the case.

I've got 2 FC adapters in a 7026-H70 risc box at AIX 4.3.3.   These are
connected to an IBM 2109 FC switch which is some model brocade.  From the
FC switch are connections to six 3590's (1 each) as well as dual
connections to an IBM ESS.   I've got DPO installed and confiured on the
AIX box.   The switch is zoned such that both FC adapter cards on the AIX
can get to the ESS, and I configured vpaths (dual pathing).   Another zone
in the switch allows only one of the FC adapter cards to reach the 3590s.

With this config, the path to the dasd throught the same FC adapter as the
3590s use constantly drops that portion of the vpath.  After rebuilding the
vpaths 6 times I gave up, thankful that I had isolated all the tape drives
to one FC adapter.

If you get any other experience PLEASE let me know.

Al Barth
(ready for another name change, but currently)
Zurich Scudder Investments




                    Jeff Bach
                    <jdbach@WAL-M        To:     ADSM-L AT VM.MARIST DOT EDU
                    ART.COM>             cc:
                    Sent by:             Subject:     Re: FC Tape Drive 
Multi-Pathing?
                    "ADSM: Dist
                    Stor Manager"
                    <ADSM-L AT VM DOT MA
                    RIST.EDU>


                    09/25/01
                    02:32 PM
                    Please
                    respond to
                    "ADSM: Dist
                    Stor Manager"






Josh,

1.      You can have 2 fiber connections per tape drive.  Each with a
separate device.  The first cfgmgr will show one path and the second will
show the second path.
2.      I believe AIX can do this with multiple device path, but I am not
sure of specifics.
3.      I would make sure to use many tape drives and watch the switch with
"portperfshow" to detect any bottom necks created with 36 tape drive on a
SAN.  Also to tell exactly the SAN device you are talking to "lscfg  -vl
rmt1"

        What advantage do you hope to gain from multi-pathing?

Jeff Bach
Home Office Open Systems Engineering
Wal-Mart Stores, Inc.

WAL-MART CONFIDENTIAL


        -----Original Message-----
        From:   Joshua S. Bassi [SMTP:jbassi AT IHWY DOT COM]
        Sent:   Tuesday, September 25, 2001 1:24 PM
        To:     ADSM-L AT VM.MARIST DOT EDU
        Subject:        FC Tape Drive Multi-Pathing?

        All,

        Does anybody know if there is any way to setup tape drives (Magstar
in
        particular) for dynamic multi-pathing?  I have a customer who is
        deploying 35 Magstar FC based drives in a SAN environment behind 2
        Brocade 6400 switches.  There will be 6 RS6K 4.3.3 TSM servers
sharing
        the drives using tape library sharing.  Each host will have at
least
2
        FC cards for tape and 2 for the disk environment.  Multi-pathing
the
        disk subsystem is easy, but I have never heard of a way to set it
up
for
        tape drives.


        --
        Joshua S. Bassi
        Independent IT Consultant
        IBM Certified - AIX/HACMP, SAN, Shark
        Tivoli Certified Consultant- ADSM/TSM
        Cell (408)&(831) 332-4006
        jbassi AT ihwy DOT com


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