Today's blade servers are by no means constrained in their I/O capabilities, said executives from industry leaders IBM and Hewlett-Packard, and make an excellent virtualization platform.
Responding to criticism of blades' limited I/O capacity
Blades have undergone a progression, Fichera said, from their earliest days, when manufacturers focused on "the most numbers of small, dense blades," to a second generation "that was the equivalent of rackmount servers," and finally, to today's third generation systems, which feature "massively scalable I/O both inside and outside."
The imminent availability of 10 Gigabit Ethernet (10GbE) connectivity should put to rest any lingering concerns. IBM announced 10GbE for the BladeCenter H in mid-January in the form of a Nortel 10G switch module and NetXen 10GbE Ethernet expansion cards.
With up to two dedicated 10GbE expansion cards per blade in the chassis, Ishan Sehgal, IBM program director for the IBM BladeCenter, said the system offers "ample I/O" to the virtualization hosts.
Hewlett-Packard has yet to announce 10GbE for its BladeSystem, but such a system should start shipping at roughly the same time as IBM's, HP's Fichera said.
Whatever the case, I/O – or lack thereof – certainly hasn't limited some shops from going all out with virtualization on their blade servers. Tom Petry, director of technology for the District School Board of Collier County, Florida, has a total of 508 HP BL35p blades in 32 p-Class BladeSystem chasses, all of which are running VMware ESX, for approximately 1500 virtual machines (VMs). About 500 of the VMs are servers, and the rest, while the rest serve up a traditional Windows XP desktops to Hewlett Packard thin clients.
Even with simple Gigabit Ethernet NICs on the blades, lack of network bandwidth hasn't been a concern for Petry. "Obviously it's going to depend on your network traffic," he said, but so far, the available bandwidth has been more than enough to handle the traffic generated by his VMs.
Meanwhile, resellers report being able to sell large blade system configurations for less than comparable rackmount servers. "I just did a quote today," said Adrian Clint, blade solutions architect with SCC, an HP reseller based in the United Kingdom, in which he was offered a 16-server BladeSystem c-Class for 15% less than 16 comparable rackmount servers.
Clint attributed the cost savings to the high levels of redundancy built in to the chassis, and shared infrastructure. For example, in the above quote, the management ports get consolidated down to two, down from 16; you need far fewer cables, transceivers, and even power supplies.
Still, users have plenty of concerns about blades, Clint said, but they tend to worry more about issues of power consumption and price than network bandwidth.
"Truth be told, so far nobody's asked me to fill a blade with the maximum number of NICs," Clint said.