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VSANs not for novices
With all of the vendor VSAN implementations, users need to be cautious about how implementations and changes are done. Only certified storage administrators should be permitted to make changes regarding what resources are shared. Inexperienced administrators may find they can easily share a storage device with another VSAN. However, they may not understand the risk of sharing an array port dedicated to only Sun servers with a Windows server on the other VSAN, or the problems of exposing a tape drive owned by Veritas NetBackup to Tivoli Storage Manager on another VSAN. Sharing mistakes may cause data corruption on the array port, or result in the tape device becoming inaccessible to either product.
Managing VSANs is an issue, too. For now, users are essentially forced back to Excel spreadsheets to track how devices are used on their assigned VSAN. And it gets even more complicated if devices are shared across multiple VSANs. Because few, if any, storage resource management (SRM) tools can track either the VSAN configuration or how the device gets shared between the VSANs, users need to understand the ramifications of device sharing using VSAN technology before using it.
VSAN technology is relatively new, so users should only logically segregate their SANs when there's a real business need. Consider Cisco's MDS 9000 or McData's DS10000 if the goal is to consolidate all of the servers and storage in one location.
For now, Cisco has an advantage because its switch has been on the market longer--administrators are certified on its switches and the technologies deployed resemble utilities in their networking switches. Brocade's AP7420 is a more viable option for sharing resources between two vendors' fabrics without compromising the integrity of either one. Regardless of the product chosen, users will be locked into a vendor's product until a standard is released in a year or so.
Bridges and routers
Not all users want to consolidate their SANs, but need to connect legacy storage devices and servers to their FC SAN. Others need to connect with off-site locations for resource sharing, disaster recovery or business continuance purposes. Storage bridges and routers can be used to satisfy these needs.
Standalone bridge and router products allow users to keep their existing technologies while connecting to their budding FC infrastructure. Cisco's SN 5428 router supports two Gigabit Ethernet ports and eight FC ports. By supporting both the iSCSI and FC protocols, users can gain access to FC-attached storage devices using low-cost Ethernet technologies. The SN 5428 also offers management features found in both the IP and FC spaces, including SNMP and VLANS for IP networks, and LUN masking and zoning on the FC side.
The Crossroads 10000 router offers users a way to extend the life of their existing SCSI-attached storage devices. In addition, Crossroads has advanced its SCSI-to-FC bridge product, the SA40, which allows users to take their legacy SCSI-attached servers and connect them to a SAN. The SA40 also offers LUN masking capabilities and the unique ability to connect AS/400s to SANs.
In addition to just connecting existing devices to SANs, products from companies such as CNT and McData allow users to connect different SANs at different geographic sites. CNT's UltraNet Edge Storage router supports FC and Ethernet interfaces; the IPS 3300 Multi-Protocol IP Switch from McData supports FC, Gigabit Ethernet, iSCSI and iFCP protocols. Both offer bandwidth management, and their routers can interoperate with any E_port-capable FC switch. This permits users to connect different brands of switches at different sites to allow procedures such as asynchronous mirroring and sharing storage between sites.
This was first published in May 2004