ADSM-L

Re: Question on FC tape drives.

2004-10-19 17:42:34
Subject: Re: Question on FC tape drives.
From: Ben Bullock <bbullock AT MICRON DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Tue, 19 Oct 2004 15:42:12 -0600
        Excellent,
        Just the kind of advice I was looking for. I was unaware of the
alternate name feature on the Atape driver. I believe I see what the
script is doing and should be able to use something similar for my site.

        Thanks,
        Ben 

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Orville Lantto
Sent: Tuesday, October 19, 2004 3:19 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: Question on FC tape drives.


Running tape through the SAN is great!  Whenever there are two or more
paths to a drive, do use alternate pathing.  The warning you refer to
applies to all devices and probably in all computers, if you change
something about the device, you had better inform the driver of the
change!

To deal with the arbitrariness of AIX device names, I use the alternate
name feature of the Atape driver.  I do this especially for HACMP
systems where the names MUST be the same on the HA nodes.  I have chosen
to build the names as "rmt."+"last 4 hex digits of WWN ." = "path
number"

 Here is a script fragment showing how I construct a name.

do
        WWN=`lsattr -El $d -a ww_name|cut -f2 -d" "|cut -c15-`
        root=`echo $d|cut -c1-3`
        new_name=$root.$WWN.0
        let "j=0"
        while [[ -e /dev/$new_name ]]
        do
                let "j=j+1"
                new_name=$root.$WWN.$j
        done
        chdev -l $d -a new_name=$new_name
done

Good Luck!


Orville L. Lantto
Datatrend Technologies, Inc.  (http://www.datatrend.com)
IBM Premier Business Partner
121 Cheshire Lane, Suite 700
Minnetonka, MN 55305
Email: Orville.Lantto AT datatrend DOT com
V: 952-931-1203
F: 952-931-1293

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Ben Bullock <bbullock AT MICRON DOT COM>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU> 10/19/2004
04:03 PM Please respond to
"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>


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Subject
Question on FC tape drives.






        Folks,

        We are moving from 3590E tape drives to 3592 tape drives. We are
also moving from a "direct attach to the TSM server" to a "attachment
through a FC switch".   I'm sure I'm not the first person to make this
change in their environment? Any hints anyone would like to share with
me?

        All my TSM servers are on AIX 5.2 and are using the latest and
greatest Atape drivers.

        As I read the documentation on the Atape drivers:


(ftp://ftp.software.ibm.com/storage/devdrvr/Doc/IBM_TotalStorage_tape_IU
G.pdf)

        I see that in this new configuration, I could take advantage of
the "Automatic failover" and "Dynamic load balancing" features.  As I
read through the document (Chapter 6), it looks like upon a path
failure, is supposed to fail over transparent to the user, but then has
this note that concerns me:

        2. The AIX operating system only supports a static configuration
of devices, which also applies to the Alternate Pathing and Failover
Support. When devices are initially configured at a specific SCSI ID and
physical connection (drive port, host bus adapter, and switch
number/port, if
applicable) and in the Available state, changing the physical device
address/connection without either rebooting or unconfiguring and
reconfiguring the devices has unpredictable results and is not
supported.

        Also, it looks like when you remove your rmt devices (say, to
upgrade the Atape drivers), it looks like the RMT devices may get
reconfigured with totally different rmt numbers, requiring a reconfigure
of the devices defined to the TSM server.

        I'm kind of an orderly guy and like to have my rmt devices
defined sequentially for ease of troubleshooting, but it sounds like it
will take some work on my end to get it to line up nicely like that.

        I will be starting my testing phase next Monday where I will
have 2 FC drives and 2 HBAs attached to the SAN. I am going to configure
the FC ports so that both HBAs see both tape drives, so I think I will
see 4 new RMT devices when I run a 'cfgmgr'.

        Anybody else set up in this kind of environment? Any
hints/helpful commands they would like to share with me?

Thanks,
Ben Bullock
Micron Technology
Boise, Id

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