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Volume management
Volume management functions appearing in the fabric continue to gain momentum. Much of this impetus comes from the fact that vendors in the host, switch and array arenas recognize that storage network traffic in enterprise environments differs from traditional networks in one important aspect: It requires a storage routing table. Network-based volume management products provide this more granular ability to map the server's host bus adapter (HBA) world-wide name (WWN) to the individual LUN on an array.

For users who manage large heterogeneous server and storage environments, network-based volume management technology should appear on their must-have list. It offers the ability to do the following:

  • Pool different vendors' arrays into one logical pool
  • Manage different classes of storage
  • Create a common storage management console
  • Enable advanced capabilities such as mirroring, snapshots and off-site disaster recovery
  • Simplify data and server migrations
What users in large heterogeneous environments need to ask themselves is if this technology should be on the switch or on an appliance dedicated to a specific function. A number of switch and storage vendors already offer this technology at the network level. Cisco offers Veritas' Volume Management and IBM's SAN Volume Controller as applications that can run on a blade in its MDS 9000 family of switches. Other vendors such as Candera Inc., DataCore Software, FalconStor, Hewlett-Packard Co. (HP), IBM, Troika Networks and Softek also offer volume management products that run as appliances in the network.

Unless users are experiencing a lot of pain managing their environment, they should wait for a standardized API virtualization interface. A standardized API will free users from being tied to any one specific switch vendor's volume management implementation and allow them to easily move between switch vendors in the future. The forecast is for a 2005 release of the Fabric Application Interface Standard (FAIS) 1.0 standard that will provide standardized APIs for network-based volume management.

For those enterprises ready to move ahead now, consider either products that are SMI-S enabled or comply with their existing environment. For users who predominantly have either Veritas or EMC in their shops, look to current or forthcoming products from Brocade, Cisco or McData which have announced plans to port these types of volume management products to their switches.

Some new technologies like Maxxan's 256-port MXV500 give users an either/or choice of virtualization technologies. In band, the MXV500 supports file-level and block-level virtualization as well as virtual tape. The switch also supports existing out-of-band products by putting what Maxxan calls "coordinating software" into the MSV500's application card that works in conjunction with existing products on the market. This functionality allows users to choose which type of virtualization solution they wish to deploy and helps remove any concerns about in-band virtualization causing congestion in the switch.

Some users view moving to network-based volume management and away from existing--and working--storage vendor array interfaces as too many steps to take all at once. To help ease users down the path, both Troika Networks' Accelera NSS and DataCore's SANsymphony can create the virtual storage pool from a number of heterogeneous storage arrays. These products run as appliances in the network and can represent LUNs to servers in the manner system administrators want to access them. They can also be deployed as point solutions, allowing users to move into them at a pace at which they're comfortable.

For example, IBM's Subsystem Device Driver (SDD) dual-pathing software looks for a volume labeled with an IBM signature before its dual-pathing functionality will work. Both Accelera and SANsymphony can present a virtual LUN to servers with the IBM 2105 volume signature, even though it may be carved out of a virtualized pool of Dell, EMC, HP and StorageTek storage. This should permit the SDD driver to work as it had before even though there may be no IBM 2105 storage anywhere on the SAN.

Cisco was the first of the major switch vendors to successfully port and host existing server and network-based virtualization technologies on a FC switch. Its MDS 9000 family of switches allows either IBM's SAN Volume Controller (SVC) or Veritas' Storage Foundation for Networks software to operate on the switch. Cisco says it intends to work with EMC and HP and is still in the investigation stage with HDS.

Porting these existing storage management technologies allows users to continue to work with products they're accustomed to using. (For more information go to http://storagemagazine.techtarget.com/804TRchart2.) IBM's SVC ships with software such as Peer-to-Peer Remote Copy (PPRC) and FlashCopy that also come with its IBM Shark. Similarly, users experienced with Veritas' Foundation Suite will find Flash Snap and integration with its Enterprise Administrator and SANPoint Control products at the network level. Users deploying these technologies on Cisco switches can experience one additional benefit. Cisco claims that deploying both its VSAN technology and one of these virtualization technologies on the same switch allows users to virtualize storage in multiple VSANs simultaneously.

On the other hand, companies such as Candera, DataCore, FalconStor, Maxxan, Softek and Sun that offer their own network-based virtualization products usually present LUNs that have characteristics unique to their products. Yet many enterprise administrators are hesitant to deploy these products throughout their enterprise, fearing that they are too risky and too narrowly focused or they are incompatible with the existing infrastructure.

As users consider the benefits and drawbacks of network-based volume management and how to best implement it, here are some key steps to take:

  • Start testing now. Whether on the switch or as an appliance, users need to spend at least a couple of months getting their arms around this technology before gradually moving it into a production environment.
  • Pick a product that fits into your environment. Network-based volume management requires a major change to your storage environment. If you're already an EMC, IBM or Veritas shop, it's probably best to choose one of their products. In a heterogeneous storage and server shop, a third-party product from a vendor such as DataCore, Softek or Troika Networks should be considered.
  • Move slowly. Network-based volume management is a foundational storage technology. It will be extremely difficult for an organization to migrate from the product once it's put into place.

This was first published in August 2004

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