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VMware pros boot ESXi off USB flash drives

Installing ESXi on memory-based thumb drives and SD cards has gained steam among forward-looking VMware administrators.

IT professionals on virtualization's bleeding edge have begun to experiment with a new method of deploying a hypervisor to a server: installing a slimmed-down hypervisor such as VMware ESXi on a USB flash drive or secure digital (SD) card.

Most VMware shops still opt to install the full version of VMware ESX -- complete with a Linux service console -- onto internal hard drives. Given rumors that VMware will discontinue the service console in the next major release, some forward-looking VMware engineers considering ESXi.

"People will need to get used to a more ESXi way of doing things," said Simon Seagrave, the author of the virtualization TechHead blog. He uses the slimmed-down ESXi in his home lab and has grown fond of it.

The case for ESXi on flash

In most cases, ESXi is installed onto a local hard disk drive, but installing it on flash is another option. ESXi fits handily on an inexpensive 1 GB drive, is supported by both VMware and the major server vendors, and is reportedly easy to set up.

The ESXi-on-flash scenario has many advantages, Seagrave said. The first is that it enables the deployment of diskless blade servers such as Hewlett-Packard Co.'s BL490c and BL495c "virtualization blades." In that case, ESXi can be installed on a USB thumb drive or on the internal SD drive.

People will need to get used to a more ESXi way of doing things.
Simon Seagraveblogger TechHead

Alternately, administrators might want to save hard disk space and compartmentalize the ESXi boot image from virtual machine (VM) images stored on larger-capacity SATA (or Serial Advanced Technology Attachment drives, and VMs' Virtual Machine Disk file format images running on high-performance SAN storage.

Another use case for ESXi on flash is remote systems deployment, Seagrave said. In the past, standing up a new server at a remote office required travel by a trained professional to the site. But now, "rather than sending someone out at great expense, you just put ESXi on a USB stick in the mail, have someone stick it in an internal USB drive, and boom, VMware is up and running."

Mark Vaughn, a VMware vExpert and enterprise architect at a national information services firm, is exploring the idea of ESXi on USB because it would simplify his VMware host setup.

"We're looking at the idea of pre-purchasing a bunch of USB thumb drives and using VMware Workstation to pre-configure them with ESXi," Vaughn said. "Then, when a new server comes in, we can just put the thumb drive in, and we're ready to go."

For Vaughn, who oversees an ever-increasing server farm of more than 100 VMware hosts, preconfiguring ESXi on a flash drive has a lot of appeal. Between bringing new servers online and performing hardware refreshes, "anything we can do to automate that and make things uniform is good."

Early days for ESXi on flash

Despite the advantages of ESXi on flash, early adopters say some kinks need to be ironed out.

For instance, TechHead's Seagrave said that HP's pre-installed internal USB drives have been known to come loose during shipping and arrive "rattling around the enclosures." HP now factory pre-installs ESXi on an SD card, which stays more securely fastened, he said.

And where Dell and IBM include an ESXi image specific to their servers on VMware's website, the HP-specific ESXi image is buried on HP's site, said vExpert Vaughn. Trivial as it may sound, finding the HP image "is one more hoop that we have to jump through," he said.

Others question how much an improvement booting off of USB flash is compared with any other external storage mechanism.

"You could argue that USB flash is just another kind of disk drive. How different is this from booting off a USB CD drive?" said Gordon Haff, the principal analyst at Illuminata Inc. in Nashua, N.H. "It may be incrementally easier, but it's a pretty small distinction."

Nor is booting ESXi off flash a true embedded hypervisor, something VMware has talked about for several years.

"We're not really talking about an embedded hypervisor in the sense of a super BIOS, where I turn on the system and I get virtualization," Haff said. "That idea really hasn't taken off like I thought it would, although that could still change."

Let us know what you think about the story; email Alex Barrett, News Director at, or follow @aebarrett on twitter.

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