Synergetic SANs and blades

InfoWorld - "Synergetic (adj): Working together; used especially of groups, as subsidiaries of a corporation, cooperating for an enhanced effect."
I like this short definition of the word synergetic because it's a good description of what happens when you join blade servers and SANs.
Obviously, dedicating storage devices to each server doesn't fit well with the cooperative nature of blade clusters. That's why they usually connect to their storage via some kind of switching device, such as a Fibre Channel switch.
However, that may change, because SAS (serial attached SCSI) -- an emerging technology that will eventually replace parallel SCSI in enterprise storage -- is acquiring new capabilities.
It's difficult to argue that SAS isn't an ideal partner for server blades, considering its well-aligned characteristics, including high scalability, small-form-factor drives, and controller compatibility with less-expensive SATA (serial ATA) drives.
But there's more: Unlike its parallel ancestor, the SAS protocol makes it possible to connect thousands of devices -- at least it does on paper. Practical real-world applications may deploy much smaller numbers, say hundreds of devices.
Now imagine an installation with blade servers connecting their storage enclosures, each mounting a dozen or so SAS drives. There's plenty of capacity there, but to attain proper switching functionality, we would have to insert Ethernet or FC switches in that configuration.
See anything wrong with this picture? Using the FC or Ethernet switches makes the setting complicated and expensive. PMC-Sierra agrees, and in cooperation with major blade vendors such as Dell, HP, and IBM, it is doing something to improve the situation by adding switching capability to its SAS adapters.
Quite a few boxes in your data center already may have been built using PMC-Sierra components or designs, so this move isn't a huge leap for the company. If you want to know more, PMC-Sierra's Web site is worth visiting, if for no other reason than to access Webinars and white papers on a variety of interesting topics, including SAS. Registration is needed.

"We recognized an opportunity to take the SAS standard and add the switching features that you would normally see in FC or Ethernet," said Mark Stibitz, vice president and general manager of the enterprise storage division at PMC-Sierra.
In fact, PMC is announcing two new products in its maxSAS line. One offers a 24-port connection to SAS enclosures and the other offers a 36-port connection. These cards will allow switched connections between blade servers and SAS enclosures. Moreover, like FC switches, they will make it possible to restrict blade servers' access to

Reprinted with permission from

For more enterprise computing news, visit Infoworld.com
Story copyright 2006 InfoWorld Media Group, Inc. All rights reserved.