Cisco is working on a new service that will enable changes to be made to a storage network without affecting the data being set across it at the same time.

When SANs are busy serving data, reconfiguring storage environments through the data path can slow the network down. Cisco is going to offer an API for its MDS 9000 switches that will allow partners' products to engage in out-of-band communications with the SAN and not disrupt data flow, the company claims.

This MDS 9000 Data Tap Service, essentially provides a protocol-based interface between the Cisco MDS 9000 SAN switches and third-party storage appliances, allowing these appliances to access servers and storage devices on a SAN without having to be directly in the path of the data.

It will be demonstrated by Cisco and three partners (Alacritus (disk-based data protection solutions), Kashya (business continuity) and Topio (data recoverability)) at Storage Networking World in Phoenix, Arizona, in early April.

The service will be available as a feature on one of the line cards for the Cisco MDS 9000 and thus for use on any of the modular chassis', namely the MDS 9216, MDS 9506 and MDS 9509.

This approach differs from having storage applications actually run on the fabric, as is the case with Brocade's FAP7420. Alacritus is porting its virtual tape application to that platform.

There are therefore two approaches with the storage switch either hosting the third-party software or, alternatively, providing a side door through which it can access the SAN. It remains early days yet - too early to say which approach is better or what the detailed features of either approach are.