Maximum disks per path

[Jim Naylor]

When we installed our EMC 8430 a couple of years ago, we were told that HP has a limitation on the number of disks it can see per path of 256 disks. At the time we had a total of about 300 disk drives split amoung 3 systems. Since then we have consolodated mostly to one N4000 system. We just filled out the box with basically another 300+ disk drives (as HP-UX SEES IT) and I was wondering if this limitation is still true and what it means "per path". We have EMC PowerPath running also. Thanks. Jim Naylor

[Yosef Rosenblatt]

Mr. Naylor,
The 256 lun limitation is no longer strictly true. The limit depends on your O/S version, Driver versions, Host Bus Adapter type, other Host configurations and possibly your Symmetrix Code Level. I would suggest that you speak to your HP and EMC technical resources for specific answers for your configuration.

The opinions expressed herein are my own and not necessarily those of my employer.
Yosef Rosenblatt

[Martin Johnson]

You are aware that this issue should have been addressed *before* you purchased the N4000, aren't you? I would suggest you talk to the sales rep who sold you the N4000 and have him/her research and provide a solution (at no additional charge, of course!)

HTH
Marty

[Sandip Ghosh]

The 256 disk limitation is for your single VG. If you are having only one volumegroup and having more than 256 physical volume, then only you will face the problem, otherwise not. I am sure that you are not putting all the disks in a single volume group.

Sandip

[Jim Naylor]

I received this information from HP hardware support. Thanks to everyone that replied.

Quoted from the sales config guide:

"There are a number of factors that lead to LUN count maximums. The device itself can have limitations, the adapter/driver pair can have limitations and the Server itself can have limitations. There are tested limits, theoretical limits and physical limits. The numbers stated in the chart below deal with th edevice limits and the driver/adapter limits. The HP-UX Operating System supports 1024 active hardware paths concurrently (i.e. LUNs that are opened). The non-active hardware paths are not counted (i.e. alternate paths are not counted regardless of the number of alternate paths)....
The hardware paths to LUNs per HBA on the systems is 512 for non-HA environment and 320 for a HA environment (MC/ServiceGuard, ServiceGuard OPS)."

"The XP512 supports 256 LUNs/port, however the NT servers can ONLY support a maximum of 26 drive letters. Clustered NT servers support 8 shared LUNs per cluster."