Hi,

I am wondering if multipathing for tape device works in same way as for fisk.

Can someone explain or provide link to any doc or wikid which explains how multipathinng works for tape devices alongwith loadbalancing.

Let me explain one strange thing which I noticed in our environment.

Four tape device connected to a switch blade port 1,2,3, and 4. So lets assume TD1, TD2, TD3, and TD4.

TD1, and TD2 are zoned to fabric F1

TD3, and TD4 are zoned to fabric F2

Filer HBA 4a is member of fabric F1

Filer HBA 4b is member of fabric F2

Now we are able to see either TD1, TD2 or TD3, TD4. Means in some cases TD1, TD2 and in some cases TD3, TD4. Looks whichever ONTAP picks up first shows only those two. If I disable HBA 4a even then I see TD1 and TD2 and /etc/messages file says TD1, and TD2 switched to fabric 2 but TD1 and TD2 are not zoned to fabric F2. So don't know why.

So then I zoned as followes

TD1, and TD2 zoned to both fabric F1 and F2

TD3, and TD4 zoned to both fabric F1 and F2

Now I see all four tape device but all are access either fabric F1 or F2. If I disable one HBA port then all tape devices switched to another HBA but doesn't balance no. of tape device across both HBAs if both are enabled.

So I was wondering for following things.

1/ How to check if tape device have two paths available and which one is primary and alternate, like for disk. i.e. "storage show disk -p"

2/ How load balancing is done for tape devices ? I expect should work based on total no. of tape devices. For disks it works based on total amount of MBs transferred across HBAs and do dynamically.

3/ Why see half of the tape devices if do load balancing at Fabric level and if zoned all tape device to both fabric then why don't ONTAP doesn't do load balancing at its own.

Thanks & Regards,
Raju