|In-band vs. out-of-band virtualization|
SPAID was developed with the intent of eliminating control path performance bottlenecks. But there's little software that takes advantage of this new architecture. At the end of 2004, the only generally available software using SPAID was StoreAge's SVM. But many
vendors are working on software that will leverage part or all of the SPAID architecture. This changeover is analogous to events in the high-performance computing market: Software had to be rewritten to accommodate the architectural change from single-threaded monolithic designs to massively parallel architectures.
Troika Networks was the first to develop a SPAID ASIC in its Accelera intelligent switch appliance, bundled with storage services from StoreAge. Those services include heterogeneous storage volume management, local and remote mirroring, replication, snapshot and data migration. Troika eliminated application server-based agents typically required for out-of-band storage network block virtualization. It worked with StoreAge and developed multipath fabric agents for the majority of operating systems.
Cisco has been working with EMC, IBM, Incipient and Veritas to provide complete SPAID solutions tied to its MDS director switches. Cisco's MDS combined with IBM's in-band SVC is available today, and has been installed at approximately 1,000 sites. Cisco has an active SPAID-based ISV program and products, including EMC's Storage Router, should be available by mid-year.
Crossroads Systems Inc., Austin, TX, has been working hand-in-hand with iVivity to deliver a SPAID-enabled iSCSI-to-SCSI gateway appliance and board that should be released soon. The unique programmability of iVivity's iDisx ASIC gives Crossroads the flexibility and performance for tape drive virtualization, making tape drives easily sharable among many servers.
Maxxan provides complete solutions in both appliances and intelligent switches. All of its current virtualization products are in-band collaborations with FalconStor (volume management, local and remote mirroring, replication, snapshot, data migration and VTL), Microsoft (Windows Storage Server 2003) and Veritas (NetBackup.) Maxxan has tackled in-band performance, scalability and reliability issues by architecting an I/O engine (as an appliance and as a blade in its director-class switch) that has high I/O, no single point of failure, high availability and can be placed in its intelligent switch. Maxxan is working with StoreAge and others to deliver complete SPAID-optimized solutions.
Maranti has developed SPAID-optimized software for its switch for volume management, local and remote mirroring, replication, snapshot and data migration McData is working with Aarohi's FabricStream SPAID ASIC to deliver intelligent switches that will be part of EMC's Storage Router program this year. Brocade has also been working with EMC and its Fabric Application Platform using the Rhapsody SPAID ASIC to deliver an intelligent switch for the Storage Router program.
When to implement
The big question is when, what and where to implement, but there is no single, easy answer. It depends on an organization's current pain, sense of urgency and risk tolerance. If storage infrastructure management is becoming intolerable, you should implement virtualization as soon as possible. What solution to implement should be based on the answers to the following questions:
- How well does the product meet the current needs of the organization?
- Will the vendor's product roadmap (scalability, performance, functionality, etc.) match the organization's perceived future needs?
- Is the product flexible enough to meet unforeseen changes in organizational needs?
- How does the product stack up for price performance, TCO and savings vs. competing options?
- What are the product's long-term OpEx costs?
- Will the organization get locked into the supplying vendor?
- How stable and mature is the product? (How strong are the customer references?)
- How will the product be supported?
- What is the organization's risk tolerance?
Where to implement is another key issue. A second-wave solution can be implemented in an intelligent switch, in an appliance on the fabric or in the array. The answers to the previous questions should point the way to the most appropriate implementation. In general, an in-band, second-wave solution will be less scalable and provide lower performance than an out-of-band equivalent. In-band solutions should be limited to small- to medium-sized implementations; out-of-band solutions can scale from small businesses to enterprises. But some products, like Hitachi's TagmaStore, challenge this conventional wisdom. Ultimately, where a solution is implemented is less important than how well it meets an organization's current and future needs.
This was first published in February 2005