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Although we didn't observe any platform incompatibilities from any of the tested products, we liked how Vinca's solution is built on the well-known and tested mirroring routines inherent in NetWare.

The only downside to this approach is the performance hit sustained when remirroring is required during re-synchronization. While configuring StandbyServer Many-to-One from the NetWare console, the mirror server exports one or more specific disk drives to each of the protected servers, which are then viewed as virtual local drives. This lets the protected server access these exported virtual local drives as valid destinations for mirroring any or all of the protected server's local volumes via NetWare's INSTALL.NLM.

This approach is significantly different from those of the other servers that we tested. LANtegrity, for instance, manages the mirroring from the mirror server itself via its own mechanisms. Those who like solutions based on existing technology with a good track record will appreciate Vinca's method.

None of the products t ested requires a dedicated or secondary network link between servers, but the installation of a dedicated link makes good sense on any segmented network with three or more protected NetWare servers--especially when you consider the nature of mirroring traffic, connectivity outages and normal LAN usage.

StandbyServer was more affected by interruptions than the others we tested. And when connectivity was restored in StandbyServer, we noticed a small--but quite palpable--performance hit while the servers resynchronized their NetWare mirrors. When dealing with multiple large volumes, this procedure can take hours. In contrast, LANshadow picked up its round-robin scanning where it left off and synchronized as a matter of course. Double-Take kept track of changes on the protected server during the outage and updated the mirror server upon reconnecting.

In our failover tests of StandbyServer Many-to-One, the transition to stand-in mode occurred smoothly following well-defined procedures in the included accompa nying documentation.

When our NetWare 4.11 mirror server stood in for our NetWare 4.10 or NetWare 3.12 protected server, the transformation of the mirror server, from its native version of NetWare to the failed server, was clean and complete. Once the downed server was returned to service, the mirror server smoothly reverted back to its originally configured version of NetWare.

Note that if you are planning to protect file servers with NetWare versions other than the version installed on the mirror server, you should boot the mirror server under those other versions prior to putting the system into service.

And, unless your hardware platforms are identical, some configuration changes will have to be made in the stand-in boot procedures on the mirror server. The install routines should handle this a bit better. Interestingly, the other automatic failover product, LANtegrity for NetWare, didn't have this problem: The original version of NetWare on the mirror server does not revert to the NetWare vers ion of the failed server.

The administrative interface to StandbyServer is the familiar text and graphics of the NetWare console screen. Although it's not as slick as the Windows interfaces used by its competitors, the tightly coupled relationship with NetWare lets you manage everything from the same location. If a separate GUI were supplied, the administrator would need to switch back to the console anytime he or she needed to examine or modify the partitions or mirrors. Vinca's interface solution, though not GUI-based, does make a lot of sense.