SAN Isolation Plans Unfold

Amid lots of talk about SAN consolidation, a small group of suppliers is working to keep multiple SANs separate.

SAN isolation, also known as fabric isolation or SAN partitioning, allows multiple SAN fabrics to interact as though they are a single SAN. The goal is to let SANs share expensive gear such as tape libraries, while ensuring many networks in a multisite enterprise don't have to be taken down in order to change configurations or perform other maintenance functions.

Sounds fairly specialized, but at least one vendor claims SAN isolation is selling briskly. According to Gregg Pugmire, executive VP of sales and marketing at LightSand Communications Corp., customers are increasingly asking for his company's i-8100A, billed as a switch that connects SAN devices without merging fabrics.

When two universities wanted to share SAN resources, for instance, one IT manager told Pugmire, "We want to share their toothpaste, but not their toothbrush." Yucky, but you get the picture: Some outfits want to maintain distinct SAN identities and even fabric vendors, but still share costly gear.

Another benefit of SAN isolation is that errors in one domain can be kept from spreading to other segments linked over a WAN or MAN.LightSand's i-8100A deploys a spec called AR/DAT (autonomous region/domain address translation) to achieve SAN isolation. It's a technique similar to network address translation (NAT) in the IP world, Pugmire says, but it's based on Fibre Channel technology.

Other vendors also are interested in SAN isolation. Cisco Systems Inc. (Nasdaq: CSCO), for instance, uses a technique called virtual SAN (VSAN) to let specific SAN fabrics exist as distinct entities -- including multivendor fabrics that may be linked to the MDS 9000 through other director switches. VSAN software comes as part of the basic software for Cisco's MDS 9000.

To allow VSANs to share storage devices, Cisco in November 2003 added a feature called Inter-VSAN Routing (IVR) to its Enterprise Package bundle, an optional product for use with the MDS 9000. Currently, the Enterprise Package is sold through just one Cisco OEM, however -- IBM Corp. (NYSE: IBM). EMC Corp. (NYSE: EMC) and Hitachi Data Systems (HDS) should start offering the bundle in this quarter, according to Cisco spokesman John Noh. Hewlett-Packard Co. (NYSE: HPQ) is expected to start shipping it in the second quarter 2004.

Brocade Communications Systems Inc. (Nasdaq: BRCD) plans to offer SAN isolation in a feature called "Logical Private SANs" announced last fall. Today, a Brocade spokeswoman says the feature is already in the hands of OEMs, which are in the process of certifying it for resale. No date has been given for its general availability, though.

McData Corp. (Nasdaq: MCDTA) also is into SAN isolation, and early on certified its switches to work with LightSand's product. But McData says its Eclipse and IPS switches, designed to sent storage traffic over IP SAN extensions, also carry SAN isolation features.McData's solutions are based on the Internet Fibre Channel Protocol (iFCP) specification, developed under the auspices of the Internet Engineering Task Force (IETF). McData has been the only switch vendor to line up behind iFCP, which it embraced after purchasing Nishan Systems last year (see McData Sticking With iFCP).

As more SAN isolation products appear, one issue will come to the fore: namely, the ability to support distinct multivendor SANs. LightSand supports switch fabrics from McData, Brocade, and Cisco in its i-8100A, but doing so is a function of working to link the AR/DAT protocol to specific switch interfaces.

Brocade spokeswoman Lee Davis says the first iterations of the company's Logical Private SAN capability will likely work with Brocade equipment, though there's nothing technologically stopping multivendor versions later on.

We'll see. Some SAN switch vendors may not want to share their toothbrushes, either.

Mary Jander, Site Editor, Byte and Switch0