To understand the impact of iSNS, it is helpful to recall that when all storage devices were directly attached to systems, the simple SCSI ID number mechanism was all that was required. Each SCSI disk or tape drive was identified by a numeric ID from 0 to 7, or 0 to 15, depending on the SCSI level being used. When Fibre Channel (FC) was introduced, a more sophisticated naming convention was required, and a storage name service, essentially a distributed database, was developed. The iSNS performs the same function, and does it in a way that is compatible with FC naming conventions. The iSNS, however, is a superset, and can include both iSCSI and FC device information.
Kuhn feels that iSNS will ease many of the initial interoperability issues between iSCSI-based products. "Initially, the iSCSI initiator code from different vendors, for example, is likely to be different," Kuhn told Byte and Switch. "The standard discovery and naming provided by iSNS goes a long way toward resolving that type of interoperability issue."
Will iSCSI replace Fibre Channel? Kuhn doesn't think so, at least not in the short term. "Certainly, iSCSI needs to grow up a little bit more. It needs to have the admin of security, which is being discussed in the
IETF but hasn't been implemented yet. So, initially, we're not a replacement for Fibre Channel SANs, and I think we'd be arrogant as iSCSI purveyors to claim that or position that way."
Kuhn sees lots of iSCSI in the market, eventually. He cites cost benefits and administrative familiarity as being major attractions of iSCSI for IT managers. "A couple of years out, when iSCSI grows up a bit, you'll start to see some migration."
Kuhn is in charge of both iSCSI hardware and software at IBM, and thus has a good handle on what IBM is doing in this arena. His group did several interoperability demonstrations with other vendors at the Networld+Interop conference this last May. Rumor also has it that IBM, which intends to be a major player in the IP storage area, will be making an announcement later this week about shipping an iSCSI appliance that scales from 108 gigabytes to 1.74 terabytes.