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Strengths and weaknesses of intelligent fabric products

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Virtualization processing
Virtualization processing can reside outside of the switch, either in a standard Intel processor or in a PBA. While they don't perform switching functions, PBAs aren't conceptually different from an intelligent switch; there's a massive amount of processing power available to run applications and to perform virtualization. As opposed to switches, PBAs:

  • Can be deployed in existing SANs
  • Cost less because they don't have intelligence on every port
  • Run multiple applications in one device

In an intelligent switch, at least the first-generation variety, only one application can run on a blade. With PBAs, you buy only the number of intelligent ports you need for the size of the SAN; additional appliances can be added as needed. The logical data path is from the host initiator to the FC switch to the PBA, and then back to the switch for transmittal to the target destination. The appliance basically runs everything on the Intel server and leaves the switching environment as is.

The players
Cisco, Maranti Networks and Maxxan Systems Inc. are shipping intelligent switches. Brocade, CNT and McData are planning on shipping theirs soon. In the general-appliance category, some of the pioneers of virtualization are DataCore Software Corp., FalconStor Software Inc., IBM Corp., Sanrad Ltd., Softek Storage Solutions Corp. and StoreAge Networking Technologies. All use an Intel server for all application processing. DataCore and Softek (based upon DataCore's source code) are the only ones that use Microsoft's NT operating system; the others use Linux.

The purpose-built category includes shipping products from Candera Inc. and Troika Networks. These typically come in a 16- or 32-port format. The primary difference between these two is that Candera delivers all foundation layer applications as an integrated suite, whereas Troika has designed its controller as a platform that can run a wide variety of third-party applications.

Recently, a number of applications originally designed for hosts (Veritas Volume Manager) or appliances (StoreAge, FalconStor and IBM SVC) have been ported to either intelligent switches (for example, FalconStor on Maxxan, Veritas VM and IBM SVC on Cisco) or purpose-built platforms (StoreAge on Troika). The replication functionality embodied in EMC Corp.'s Symmetrix Remote Data Facility and the virtualization functionality in Symmetrix will be ported to several, perhaps all, intelligent switches in the near future.

Applications that work best in a central location and those that require significant movement of data from one type of storage device to another should be moved to the fabric. The biggest advantage that fabric has over other methods is that it sees everything connected to it.

Those applications include mirroring, replication (synchronous, semisynchronous and asynchronous), snapshots, storage virtualization and volume management, including LUN masking. In addition, many backup and restore and archive applications will gain from being in the fabric. It's best not to provide network-attached storage (NAS) file services from the fabric because of their reliance on a local file system; NAS heads can be connected to the fabric that delivers virtualized storage to them. The movement of applications to the fabric can be a big step toward implementing information lifecycle management (ILM).

An intelligent switch from Cisco may not interoperate with one from Brocade, except in a rudimentary fashion. The Fabric Application Interface Standard (FAIS) is a developing standard that will make interoperability a reality, but don't expect compliant products for at least another year (see "The state of standards"). Whatever product you pick, it must be able to interoperate fully with your existing SAN(s). In that regard, appliances and PBAs have a big advantage over intelligent switches: They work with all popular layer-2 switches and also bring applications to heterogeneous islands of SANs.

This was first published in October 2004

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