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But booting blades off an IP SAN has proved difficult; the one software-based iSCSI initiator for Windows that supports booting from a SAN -- emBoot's netBoot/I -- doesn't work properly with BladeCenter. Hunt is shipping a BladeCenter to emBoot in hopes that it can work out the bugs. "I really want this to work," he says.
Hunt isn't alone. Vendors also hope the booting issue can be resolved.
Disk drives are "the only mechanical thing on the blade, and mechanical things fail," says Tim Dougherty, director of IBM BladeCenter marketing. Disk drives also consume power, impede airflow and inhibit density. "The right thing [to do] is to get the disk off the blade," he says.
Compounding Hunt's boot-from-SAN problems was that there were no iSCSI adapters in a blade form factor until recently. iSCSI adapters, which allow you to toggle the boot order, have emerged as the de facto way to boot from an IP SAN.
This summer, QLogic introduced an iSCSI adapter for IBM BladeCenter. The SANblade QMC4052 is a 1 Gb/sec NIC that offloads TCP/IP and iSCSI processing, and is available for Windows, Solaris or Linux. QLogic wouldn't comment on whether it's developing an iSCSI host bus adapter (HBA) for blade vendors like Dell and Hewlett-Packard, but according to Frank Berry, QLogic's VP of corporate marketing, "HBAs with the capability to offload both iSCSI and TCP/IP processing ... will be useful in any blade server supporting external iSCSI storage."
But given a choice, Hunt would rather boot diskless using a software initiator. Assuming a blade costs approximately $1,400, Hunt would "rather not spend 50% of the cost on an HBA. It seems kind of silly."
Ease of serviceability and management are some of the reasons people choose blades, says John Humphreys, research director at IDC, and he agrees that diskless blades are an important component to that. But today, even though the attach rate for network storage blade servers is double that of regular servers, the vast majority (more than 90%) of blades still ship with a boot drive. "Boot from SAN is a great idea," says Humphreys, "but it's not exactly sweeping the end-user community."
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This was first published in October 2005