TSM Multipath

[sasha]

Hi
Can somebody help me to configure multipath for tape devices .I have enabled the failover path for them , so i have :
rmt0 Available 00-08-02-PRI IBM 3592 Tape Drive (FCP)
rmt1 Available 02-08-02 IBM 3592 Tape Drive (FCP)
smc0 Available 00-08-02-PRI IBM 3584 Library Medium Changer (FCP)
smc1 Available 02-08-02 IBM 3584 Library Medium Changer (FCP)
now how can i define drives and paths in TSM itself ? If i point them to rmtX or smcX devices where is the multipathing ?

 

[chad_small]

Read this!

So once you show both the primary and alt devices it looks like the PRI device is the once you path since I believe it is the virtual device and the alts are the two paths that the OS will load balance across behind the scenes. At least thats how I see it since you can't define the path twice to TSM. From what I see of your situation it doesn't look like you have the IBM device drive setup correctly for multipath I/O.

 

[heada]

With the correct version of atape, AIX will do the multipathing automatically. You have the correct version or you wouldn't see the PRI and ALT in the device location strings. This will work for your 3592 drive. Define the PRI connections to TSM and leave the ATL connections alone. The SMC connections are for the library itself and the atape driver doesn't automatically give multipathing for thing. To enable that, you should enable SANDiscovery within TSM. It should update the path automatically for the library if the primary path is unavailable. Again, use the PRI drive when defining them to TSM.

-Aaron

 

[sasha]

Reply

Thnxs guys
After some corrections it's look like :
rmt0 Available 00-08-02-PRI IBM 3592 Tape Drive (FCP)
rmt1 Available 02-08-02-ALT IBM 3592 Tape Drive (FCP)
smc0 Available 00-08-02-PRI IBM 3584 Library Medium Changer (FCP)
smc1 Available 02-08-02-ALT IBM 3584 Library Medium Changer (FCP)
but i still wonder if the path for TSM defined like :
Library -> device 3584 Library -> /dev/rmt0 how ( if ever ) it will auto update failed path from /dev/rmt0 to /dev/rmt1 which is ALT path even when SANdiscovery enabled ?

 

[heada]

For the tape devices (rmtx) AIX and the atape driver will control it. TSM will make a request to AIX to mount a tape in /dev/rmt0 but if that device is unavailable, AIX will mount it in /dev/rmt1 and tell TSM to that it is done. Since the atape driver allows both device files (rmt0 and rmt1) to read the same physical device, it will work and TSM will not know the difference. This is also how AIX does load balancing between connections.

The smc0/smc1 device is different. In this case, TSM will make a request to the library (smc0) but if the primary connection has failed, TSM will search the SAN on other connections (smc1) for the same device. Once it has found it, it will update the path automatically. This is what SANDiscovery does.

-Aaron