Sun began to flesh out its server/storage convergence strategy last week when it unveiled a framework for turning its OpenSolaris servers into storage arrays with a utility called the Common Multiprotocol SCSI target for Solaris (Comstar).
The first edition of Comstar, available for the Build 90 version of OpenSolaris and scheduled to become part of the general OpenSolaris distribution in its next major release in November, allows customers to create a Fibre Channel array using a repurposed server and Fibre Channel host bus adapters (HBAs), according to Scott Tracy, director of storage platforms for Sun's software group. So far, Sun has qualified HBAs from QLogic and Emulex.
Comstar brings the SCSI command set into the OpenSolaris kernel, rather than letting it run in "user-land" above the operating system. According to Tracy, this can help with the target's performance because it doesn't have to traverse the operating system and application memory for I/O to disk. However, Comstar does use some of the server's CPU, which might cause a performance hit over a typical Fibre Channel device, depending on how it's deployed.
Tracy admitted that the initial support for Fibre Channel may not be much more cost-effective than a pre-packaged Fibre Channel array because it requires two Fibre Channel HBAs (one in target mode), SAS or Fibre Channel disk, server and software. "We also plan to offer FCoE, iSCSI, iSER and SAS," which will be more cost-effective because they can be based on software, he said. "And with this Fibre Channel configuration, you can avoid paying for features you don't need, like you do with proprietary arrays."
Sun has further plans for the Fibre Channel target, including the creation of multiprotocol arrays based on its servers once the other protocols are integrated into Comstar. In addition, Comstar will eventually allow concurrent multiprotocol access to LUNs, Tracy said. While there are other items on the roadmap that pushed Sun to support Fibre Channel first, Tracy declined further comment.
"This is the execution stage of Sun's server/storage convergence strategy," said Illuminata analyst John Webster. "Their future plans probably have something to do with their flash strategy as well." Sun outlined plans for prepackaged hybrid devices when it announced support for flash disks two weeks ago.
Tom Trainer, an analyst with Analytico, pointed out a downside to Sun's Comstar strategy: the potential performance hit of sharing the CPU. Another possible caveat is that, according to Tracy, Sun won't issue a new warranty for server hardware repurposed for storage.