Virtual server SANs: FC vs. iSCSI vs. NAS

February 8, 2010 – In the beginning, most virtual server environments relied on either Fibre Channel SANs or direct-attached storage (DAS). As the virtual environments grew, end users quickly found out that DAS wasn’t going to cut it. Fibre Channel remained king for awhile (and still is), but iSCSI – and NAS – appear to be coming on strong.

In mid-2009, we polled infostor.com visitors regarding what type of storage network protocol they were using in their virtual server environments:

The question: “If you have virtual servers, what is your primary storage configuration? (check one)”

The results: 53% cited Fibre Channel SAN; 28% iSCSI SAN; 10% NAS; and 9% DAS.

A recent report from Forrester Consulting, based on a survey commissioned by Dell (no doubt the EqualLogic crew), suggests that iSCSI – as well as NAS -- is narrowing the gap with Fibre Channel. Forrester surveyed 200 IT storage decision-makers.

The question: “What storage network protocol(s) are you using (or plan to use) for your virtual server environment? (select all that apply)”

The results: 59% Fibre Channel, 57% iSCSI, and 52% NFS [NAS]. Almost a dead heat. (3% of the respondents are using non-networked storage; e.g., DAS.)

In addition to the impressive showing of both iSCSI and NAS, a key conclusion here is that end users are obviously using a mix of storage protocols in their virtual server environments.

There was, however, one seeming inexplicable anomaly in the results to that Forrester survey question: 33% cited FCoE. I’m at a loss to explain that, but here’s the explanation from the report’s authors:

“FCoE interest appears very high. There may well be some confusion regarding the adoption of FCoE, as anecdotal evidence suggests that the 34% current usage number [referring to another question] is very high for this emerging protocol. Products are just now coming onto the market and are usable only for the server side of storage networking, aggregating traffic in top-of-rack and edge switches. The reality here is likely that respondents have interest in or plans to move forward with FCoE, but have not yet implemented FCoE in such high numbers.

Confusion with FCIP, used to carry FC traffic over the WAN for distance replication, may also be increasing the adoption rates reported in this survey.

Another area of confusion relates to the adoption of 10GbE. Respondents who stated that they currently have FCoE in place in the quantitative survey revealed in interviews that they actually have 10GbE for file data traffic but are not using FCoE equipment. Suffice it to say that interest in FCoE is high at this point, but confusion about what really constitutes FCoE is clouding the adoption picture.”

Back to Fibre Channel, iSCSI and NAS: Not surprisingly, use of these protocols in virtual server environments varies by the size of the organization. For example, 70% of large enterprises (1,000 or more employees) cited Fibre Channel, compared to 50% of the SMBs.

66% of the SMBs cited iSCSI, compared to 47% of the large enterprises. And 49% of the SMBs cited NFS, compared to 57% of large enterprises.

The full report is posted on Dell’s site: “Benefits Of SAN/LAN Convergence: Evaluating Interest In And Readiness For Unified Fabric,” is posted on Dell’s site.

If you’re struggling with the storage challenges associated with rapidly growing virtual server environments, consider attending our Webcast, “Managing VM Sprawl and Reducing Costs with Disk Archiving,” tomorrow (Tuesday), February 9 at 10:00 PST, 1:00 EST.

You can get a description of the Webcast and register HERE.


posted by: Dave Simpson

Dave Simpson, Editor-in-Chief
by Dave Simpson

Dave Simpson has been the Editor-in-Chief of InfoStor since its inception in 1997. He previously held editorial positions at publications such as Datamation, Systems Integration, and Digital News and Review. He can be contacted at dsimpson@quinstreet.com

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