2 hbas see the same ports on the XP512 SAN

[ionic_tease]

The output of my cfgadm -al commands shows two of my fcal cards and they both have the same pair of assigned ports from the SAN.

Output of cfgadm -al
---------------------------------------------------
c2 fc-fabric connected configured unknown
c2::x0060x800xxxd300 disk connected configured unknown
c2::x0060x800xxx310 disk connected configured unknown
c3 fc-fabric connected configured unknown
c3::x0060x800xxxd300 disk connected configured unknown
c3::x0060x800xxx310 disk connected configured unknown

Checking format and cfgadm -al -o show_FCP_dev shows the luns from the XP up two times. Why is this? I would think that if a user was to see all these extra "spare" disk in format they would be tempted to use it up and cause a diaster!

[Ben Dehner]

Which HBAs can see which SAN ports depends on the zoning configuration in the SAN switches and the LUN masking in the XP512. You *can* present a LU to only one HBA of a host. You *can* configure switch zoning so that not all HBA's see the storage array.

However, you really want all of your HBA's to see all of the SAN ports, and the LUNs for that host available to all of these ports. This allows failover/load balancing software, such as SecurePath, PVLinks, or PowerPath, to work properly. If any component fails there are other access paths to the LU. If everything is working, you have better performance using multiple paths.

As for confusing a user, if they don't know how to configure a system for multi-path access to a disk array, they shouldn't have privileges to administer the system. (Or the system shouldn't be SAN attached.) If the system doesn't have multi-path capabilities, such as one of the above packages, then either you have to adjust the zoning or LUN masking so there is only one path, or do a very careful manual configuration of the system to avoid problems.

[ionic_tease]

So would multi-pathing software negate the ability to see 2x luns with two HBAS? It looks like both hba see two separate paths to the luns on the SAN but on the host side the luns are showing up double.

[Rob Leadbeater]

Hi,

Yes. Multi-pathing software will "mask" all the extra paths to the disk from the OS, so that it will appear as a single LUN.

Cheers,

Rob

[Ben Dehner]

The details of what the multi-pathing software does, and what you see from the host, is a little different from vendor to vendor. With PVLinks on HP-UX, from the surface it looks like you have multiple LUNs presented to the system, but beneath the covers you will see the "extra" LUNs marked as an "alternate path". With EMC PowerPath, it looks like you only have one LUN presented to the system, but, looking underneath, you see the multiple paths to get there.

[ionic_tease]

Thanks!