A recent version of Atape is required for dual path support. We use
Atape 8.3.1.0.
You also need to enable alternative pathing support on the rmt device which,
I think is set to off by default:
i.e. chdev -l <device> -a alt_pathing=yes
Then when you make the devices available to the host you will notice
twice the number of drives. If you look at the device attributes with
lsattr -El rmtx
you will notice the location code xx-xx-xx-ALT or PRI ,
the primary device value and the WWN. The latter will be 0xnnnnnnnnnn4nnnnn for
the primary device and 0xnnnnnnnnnn8nnnnn for the alternative device.
These allow you to 'pair' up the devices.
If you have more than 3 or 4 tape devices I would recommend you employ a naming
convention to the devices to make these pairs more transparent, by renaming them
after cfgmgr has brought them into the system.
Thus, we do a rmdev -l <rmtX> ; chdev -l <rmtX> -a new_name=rmtY
such that the secondary / Alternative device name is 50 greater than primary
device name - i.e:
rmt2 => rmt52
rmt3 => rmt53 and so on.
Note that errpt will log errors against both device names, depending on which
interface the drive was being accessed when the error occurred.
Finally, our experience tallies with Steve Harris' - failover is seamless
- we pulled the active cable from a drive while backing up (test !) client
data to tape and the backup carried on over the other path. TSM didn't blink.
We subsequently audited the tape and all was OK.
Regards
-------------------------------------------------------------------
Ian Smith
Oxford University Computing Services, Oxford, UK.
-------------------------------------------------------------------
~>Mime-Version: 1.0
~>Content-Transfer-Encoding: quoted-printable
~>Content-Disposition: inline
~>Date: Tue, 18 Nov 2003 08:48:41 +1000
~>From: Steve Harris <Steve_Harris AT HEALTH.QLD.GOV DOT AU>
~>Subject: Re: 2 fibre interfaces per drive
~>To: ADSM-L AT VM.MARIST DOT EDU
~>X-Oxmail-Spam-Status: score=0.0 tests=
~>X-Oxmail-Spam-Level:
~>
~>Joni,
~>
~>Later versions of the Atape driver support dual pathing and failover.
~>Once set up, AIX defines two RMTn drives for each physical drive, one with a
device path ending in -PRI and the other in -ALT.
~>
~>As I understand it rudimentary load balancing is done - when the tape is
opened, the least busy path is used.
~>
~>Failover is also neat. I was running the tapeutil test command and
deliberately varied off the adapter in use. The io just picked up where it left
off on the other path.
~>
~>See the Totalstorage Tape Installation and Users Guide, available from
ftp://service.boulder.ibm.com for details
~>
~>Steve Harris
~>AIX and TSM Admin
~>Queensland Health, Brisbane Australia
~>
~>>>> Julian.Armendariz AT HBFULLER DOT COM 18/11/2003 7:13:13 >>>
~>IBM 3590 and 3592 drives have 2 fibre interfaces. I am unsure how to
~>manage the multipathing yet, but we are going to look at configuring our
~>3590H drives that way next year to eliminate that single point of
~>failure. Our TSM server is running AIX 5.2ML2 which is connected to a
~>3494 library with 4 3590H drives which are connected to a Brocade 2800.
~>
~>
~>Julian Armendariz
~>System Engineer - UNIX
~>H.B. Fuller
~>(651) 236-4043
~>
~>
~>
~>>>> joni.moyer AT HIGHMARK DOT COM 11/17/03 12:48PM >>>
~>Hi everyone!
~>
~>We are in the process of formulating an AIX environment instead of our
~>current MVS TSM environment. We would have 2 TSM servers (one being
~>the
~>library manager) with 2 directors, 8 lan-free clients and 24 tape
~>drives,
~>which we hope to share between the 2 TSM servers. We would like to
~>have 2
~>fibre interfaces per drive in order to eliminate a single point of
~>failure.
~>My question is, how does TSM know which path it is using to the drive
~>and
~>how does it know that one of the paths to an individual drive is
~>already in
~>use? Is there software out there to manage this or is it done through
~>the
~>hardware configuration? If anyone has any suggestions I would
~>appreciate
~>it! Thanks!
~>
~>
~>***************************************************************
~>Joni Moyer
~>Highmark
~>Storage Systems
~>Work:(717)302-6603 **New as of 11/1/03
~>Fax:(717)302-5974
~>joni.moyer AT highmark DOT com
~>***************************************************************
~>
~>
~>
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