On Wed, May 16, 2001 at 12:49:40PM -0700, Fox, Adam wrote:
It is suggested if you are hooking up a dual path loop that the B loop start at the opposite end of the loop as the A loop. In other words, the B loop starts on the last shelf on the A loop and works it's way back.
Why is that loop configuration suggested?
Since the FC9 shelves are self-terminating, it would make sense to run the loops in opposite directions -- that way if there is a failure in a shelf, you'd maintain connectivity around the broken loop.
IE:
A Filer +-------------- A B | | +Shelf 1+ | | | | +Shelf 2+ | | | | +Shelf 3+ | +---------+
If shelf2 flips out, you s3 is still visible on loop B, and s1 is visible on loop A. (continue example for n number of shelves, and it still holds).
As nice as this is, I'm not sure how much it really accomplishes, since if you lose a shelf worth of disks, its probably going to equate to a double disk failure in atleast one volume, taking the filer offline anyways..
Has this behavior changed in the last year or so? Can the filer mark a 'dead' volume as such and continue serving the surviving volumes? (at worst with perhaps a reboot after one dies to reset hardware?) Obviously this would change in the case of a cluster, where it'd be better to go offline altogether and let the partner give a shot at using the disks..
Just a thought...
..kg..