The real tale of scalability rests with the fact that the chassis themselves are just sheet metal, a backplane, and some fabric ports. There are no smarts in the chassis, which makes them cheap. That coupled with the significant scaling of the FIs means that the more chassis you add, the cheaper the solution becomes. If there's a single lesson to take away from UCS, it's that the chassis are nothing more than extensions of the FIs, and they have more than enough bandwidth to run whatever you need. That said, once you've filled up a pair of FIs, you have to start over with a new cluster; different UCS clusters cannot intermingle under a single management domain as of yet.
To be frank, the features, scope, and breadth of the UCS offering is quite impressive for a 1.0 release. That's not to say there aren't problems. For one thing, it's not terribly clear when changes made to service profiles will cause a blade to reboot. In some instances, warnings are issued when configuration changes may cause a blade to reboot, but otherwise the state of a blade is somewhat opaque.
I encountered a few minor GUI problems and one more significant glitch: During one service profile push, the PXE blade prep boot didn't happen. A manual reboot of the blade through the KVM console got everything back on the right track, however. Throughout all the buildups and teardowns of the blades, this was the only time that happened.
Of some concern is the fault monitoring aspects of UCS. For instance, when a drive was pulled from a RAID 1 array on a running host, the event failed to throw a fault showing that the drive had failed. However, it did produce a notification that the server was now in violation of the assigned profile because it only had one disk. Further, re-inserting the disk cleared the profile violation, but produced no indication of the RAID set rebuild status. Indeed, there doesn't seem to be a way to get that information anywhere aside from a reboot and entry into the RAID controller BIOS, which is somewhat troubling. Cisco has filed a bug related to this problem and expects it to be fixed in an upcoming release.
A minor consideration is that, while Cisco is agnostic as to the make of the FC SAN attached to UCS, it must support NPIV (N_Port ID Virtualization). Most modern FC SANs shouldn't have a problem with this, but it is an absolute requirement.
Finally, there's the matter of cost. In keeping with all things Cisco, UCS isn't terribly cheap. Unless you're planning on deploying at least three chassis, it may not be worth it. The reason for this is that the chassis are relatively affordable, but the FIs and associated licenses are not. However, the scalability inherent in the UCS design means that you can fit a whole lot of blades on two FIs, so as you expand with chassis and blades, the investment comes back in spades. A well-equipped redundant UCS configuration with 32 dual-CPU Nehalem E5540-based blades with local SAS drives and 48GB of RAM each costs roughly $338,000. But adding another fully equipped chassis costs only $78,000, nearly half the price of a traditional blade chassis with similar specs.
I certainly found some problems with UCS, but they float well above the foundation, which is equally impressive for its manageability, scalability, and relative simplicity. There's a whole lot to like about UCS, and the statement it makes just might cause that revolution.
This story, "How Cisco UCS reinvents the datacenter," and the companion review, "Test Center review: Cisco UCS wows," were originally published at InfoWorld.com. Follow the latest development in Cisco's Unified Computing System, blade servers, hardware, and virtualization at InfoWorld.com.
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