> I am trying to set up 2 HBAs or 1 HBA with 2 ports on a server to have
> failover capability. I know about 2 software solutions: Compaq Secure
> Path, and Veritas Dynamic Multipath (Volume Manager). Can someone
> tell me about their experience on performance (speed to failover) and
> Is there any other software solution? For hardware, I know QLogic HBA
> has its own failover driver. Is there any other good alternatives?
There are a few others out there... What disk array do you have the
servers attaching to? HDS/EMC/HP have them for their Lightning,
Clariion/Symmetrix, XP/VA disk array's respectivley. They all roughly
work the same way. Veritas I understand support failover between
heterogeneous arrays, although any of the listed software shown above
will probably work given that it needs to see 2 or more paths to a
single target - but you're vendor may not support it!
From what I've seen, the failover is totally transparent for
applications and a log is generated. For example, if your doing a
huge copy from one volume to another, there is a slight pause and the
copy continues as if nothing has happened. Depending on some
applications, you may need to increase their timeout values to
accomodate the failover time, however at the OS level (Windows), from
what I've seen there doesn't appear to be any low level adjustments
Most (if not all) will also provide load balancing, some will allow
you to tweak the load balancing policies to optimize your performance.
You may want to make sure that whatever you decide to choose (i.e. the
one supported for the disk array your running) supports clustering
environments. It would be nice to know that a multi HBA server only
fails-over the HBA's within the same node in the cluster, rather than
trigger a system wide cluster failover scenario if that node's path to
the data store is interrupted.