Since you are using the Compaq branded switches, I assume you have a license for "QuickLoop" for the switches. The Compaq's are usually re-branded Brocade Silkworms. One option is to connect a hub to a QuickLoop port and have access to all your tape devices from that "QuickLoop". Your tape devices will share the bandwidth for that "looplet" but you will only have to use one expensive fabric port to enable access to all your tape devices.
The Brocade switch with a QuickLoop license can operate in three modes. Fabric mode, which is the default, hub emulation mode, where the entire switch acts like a hub (up to two switches can participate in a QuickLoop) or mixed mode, where you can enable some of the switch ports as "looplets," that participate in the "QuickLoop." QuickLoop has a nice side benefit, in that all the FC-SW devices can translate into the loop and access the FC-AL devices within that loop. This means that another option is you can add your four tapes drives to four separate ports and have point to point access to them from the servers through the fabric. Each "looplet" in the QuickLoop provides 100MB per second access through the switch to each looplet. The switch will map the FC-AL IDs to WWN names so the FC-SW servers attached to the fabric can see them in the QuickLoop.
Check with Compaq for support on your SAN configuration for your backup software and the tape drives you are using. A Compaq "Enterprise Backup" solution is what you are looking to achieve.
You can find more documentation on "QuickLoop" on Brocades Web site at: http://www.brocade.com.
As far as the Compaq controller crashing when changing your zoning, you need to keep in mind the supported SAN configurations from Compaq. Follow the guidelines on when you need zoning and what and how many nodes are supported in each zone. (There used to be a 64-node nameserver limit with older versions of the HSXXX firmware.)
Your StorageWorks controllers pull WWN information from the switches when attached to a fabric to make LUN masking an easy process. You may have "old" and unused WWNs in the controllers list. Delete these unused connection names from the controllers WWN name list to keep the list confined only to those servers that need access to that array. You may also be able to upgrade your controller firmware to the latest version to alleviate this problem.
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