active/active controllers and autopath on HPUX

[Joseph Farinaccio_1]

Using SecurePath 3.0F, and have installed for active/active array (EVA8000s). Since there is no lun masking, once we set the load balancing policy for a LUN with autopath set -l -b , which device file should be used to build VG's? We have 8 distinct paths to each LUN.

Also, what is the difference between the autopath set -l and the autopath set_lbpolicy ?

[Pat Obrien_1]

you should upgrade to sp1 for hpux first.
I see not difference in set -l wwid -b and set_lbpolicy from my testing.

On the device path question, theoretically it does not matter, but this is a subject you could write a book on. I wouold first perform a dd read of each of the 8 device files for a count of 200mb 1024 blocks within the time command to determine which 4 will be 40-42% faster than the other 4. I would use a fast path myself, though in my testing, I could not measure much difference. What load balancing policy will you use? RR SST SQL. They are each interesting in their own right.

[Joseph Farinaccio_1]

Any of the device files (mulitple paths)that point to a single LUN can be used to pvcreate, vgcreate, etc. When any one of these device files are used, Autopath will adopt the load balancing policy specified and apply it 'under the covers' to all of the associated paths. So, if you have 4 paths to a LUN and you create a volume group using only one cXtYdZ value, your preferred load balancing policy (round robin, for instance) would ensure that all four paths, even though they are not explicitly part of the volume group definition, will be used.

However, 2 best practices were mentioned. 1- be sure to include at least one path (device file) from each installed FC HBA when creating the volume group. 2- Add all the remaining paths to the VG to protect from unwanted "pvcreates" of already established volumes. By adding all the device files, you minimize the risk that someone will accidently 'discover' an unused disk drive by mistaking the alternate path for an unpopulated drive.

Thanks to Lief at the response center.

[Pat Obrien_1]

If you are picky about the order, vgscan resets to hba order the device files in the vg.