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For users who want to share resources among different SANs, but are reluctant to do a forklift upgrade or introduce a new FC vendor, Cisco is working to eliminate interoperability issues with the other two primary FC director vendors. Its MDS 9506 and 9509 FC directors support Brocade in native mode, and Cisco says it's working on supporting McData in native mode as well. With this approach, the only major features that will be lost are Brocade's and McData's advanced ISL aggregation features. This will only become a major issue when performance between the two different vendors' SANs is a significant concern.

Brocade's LSAN technology is similar to Cisco's VSAN and InterVSAN routing features, but Brocade takes a modular instead of a bladed approach using its SilkWorm AP7420 Multiprotocol Router to deliver this functionality. Like the VSAN and InterVSAN routing technology, the AP7420 logically isolates SANs while giving users the ability to share specific devices in one SAN with other logical SANs. The best fits for organizations considering Brocade's AP7420 are:

  • Users who plan to continue using either departmental Brocade or McData switches, but who need to access or share specific resources between those different SANs.


  • Companies that want to start isolating SANs with an appliance, but want to grow to a bladed FC director. The AP7420 appliance allows enterprises to isolate SANs inexpensively and to migrate to Brocade's upcoming

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  • intelligent blade for its SilkWorm 48000.


McData uses a couple of different methods to tackle SAN isolation. To connect isolated FC and iSCSI SAN fabrics to one central fabric, it takes a modular approach with the firm's Eclipse 3300 and 4300 multiprotocol SAN routers. However, the Eclipse products support only 802.1Q Virtual LAN (VLAN) and metro SAN (mSAN) capabilities. While this allows for connecting SAN islands into a central SAN fabric, it lacks the ability to expose specific SAN ports, such as those from backup servers or virtual tape libraries, to certain devices on the other SAN.

McData's i10K director is the only director that supports hard partitioning. Unlike logical SAN isolation techniques, hard partitioning is done at a physical rather than a software level on the director. Configurable on a per-line-card basis, each line card may be its own virtual SAN or multiple i10K line cards may be combined to configure a larger virtual SAN. Each of these configurations can run different versions of microcode, which allows a storage administrator to test new microcode on a partition before rolling it into production. However, the i10K suffers from the same fundamental flaw as the Eclipse products because it doesn't allow partitions to share selected device ports and route traffic between them.

This was first published in February 2006

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