The discussion of where storage virtualisation intelligence should reside has been going on for a while. As you may remember, three opposing theories suggested servers, network devices, or storage devices as preferred platforms for those virtualisation services.
To be perfectly candid, each party involved had (or should I say, still has) some very good reasons to support its thesis, not to mention a portfolio of legacy solutions to defend.
Well, apparently that attitude is changing faster than you can say "storage virtualisation," because the network storage services recently announced by Cisco Systems at CeBit 2005 and dubbed the SSM (Storage Services Module) are capturing the attention of many storage vendors.
I can't help noting that all three positions on storage virtualisation are represented among those vendors, which could suggest that some companies were opposing the network-centric theory only because a good platform to host those services was not yet available.
Whatever the reason, a convergence of support of network-centric services on the Cisco MDS 9000 by many major vendors, including EMC and Veritas Software, is good news for customers. Customers will be able to choose between competing storage applications that run on the same platform, much as they do with business-oriented applications such as ERP and CRM.
Each vendor will provide specifics for its own products, but there are essentially two ways of taking advantage of the new module: with applications entirely resident on the Cisco MDS 9000 switch (both fabric and director models can be equipped with the SSM) or by invoking services from applications hosted on a separate box.
An example of the first approach comes from EMC, which demonstrated its long-awaited Storage Router at the CeBit show, but keep your eyes open for more switch-hosted applications to follow.
The second approach calls for a little more explaining. In essence, vendors that manage critical data protection tasks (such as snapshots and replicas running on custom hardware) can invoke network services on the switch while maintaining most of the business logic on their appliance.
How do they do that? The hook to SSM services is a Cisco protocol called SANTap, which enables a compliant application residing on a different box to intercept and appropriately direct data frames to a selected storage device.
Kashya, maker of the KBX5000 Data Replication appliance, is among the first vendors to release a SANTap-aware version of its product. Mehran Hadipour, Kashya's vice president of marketing, explains that the appliance protects data locally or remotely across heterogeneous storage systems and offers virtually unlimited recovery points.
Without an SSM, Hadipour says, the KBX5000 has to rely on server-based agents to capture data to replicate -- agents that are expensive to develop and maintain. The SANTap approach removes the need for those server-based agents and extends the data-protection target range to all networked storage visible from a Cisco switch, says Hadipour, while removing any possible server-induced latency from the data path.
In addition, Hadipour states that when deploying the SANTap version of the KBX5000, customers won't have to install anything on their servers. This should reduce the need for downtime and the risk of inconsistencies with future OS updates.
Another storage player, Xiotech Corp., well know for its Magnitude 3D SAN appliances, will offer a SANTap-compliant version of its TimeScale replication appliance. According to Neville Nandkeshwar, Xiotech's director of solutions marketing and strategy, Xiotech is the first vendor to include SSM and SANTap in a comprehensive SAN solution.
In the months to come we'll probably hear a lot about reduced latency over server-based data transfers because vendors of major backup applications are already jumping on yet another feature offered by the SSM. The SCSI-2 Extended Copy offers the possibility of speeding up backups using the Cisco switch, rather than a server, as data ramp.
Another service offered by the SSM, Fibre Channel Write Acceleration, promises to expedite remote synchronous replication regardless of the type of WAN transport, which can be dark fiber, DWDM (dense wavelength division multiplexing), or SONet.
It's nearly impossible to recap all the possibilities that Cisco's SSM brings to the storage networking table in one meaningful sentence, but one thing is certain: The new module not only fills a space left empty for too long, it also focuses the attention of many vendors on ready-to-deploy storage services.
Plus, we may no longer hear any philosophical debates on where virtualization should reside, but only more practical discussions on which storage solution better fits the business requirements. That in itself is an improvement in my book.