Announced more than two years ago, VMware Inc.'s slimmed-down ESXi hypervisor has finally gained traction among shops that have updated to vSphere, although many legacy shops are in no hurry to migrate from ESX.
VMware Inc. has stated that its direction lies with ESXi, but the vast majority of existing VMware shops still use the full version of ESX, which features a Linux-based service console that can be used to install agents and run scripts.
"We look at ESXi as a proof of concept to see what it can do on blades," said a senior systems administrator for a Fortune 500 retailer, "but in terms of troubleshooting and ease of use, the ability to open up the service console and work on the box directly is useful." Most of the administrators on his team have a Linux background, and "we like to stick with what we're comfortable with."
ESXi a painful migration for some users
Resistance to ESXi is especially strong in shops that run scripts and agents directly on the service console, said Ron Singler, a VMware and storage consultant at a national IT integrator.
Organizations with scripts to automate server provisioning, for example, will need to rewrite them to work with the vSphere Management Assistant (vMA), a Linux virtual machine that replaces the scripting capabilities provided by the ESX service console. That can take up to a couple weeks of developer time to do well, Singler said.
By extension, organizations that make heavy use of PowerShell and VMware's PowerCLI may have an easier time adopting ESXi. That was the case with Stuart Radnidge, a virtualization architect for a large global financial services company and blogger at vinternals.com. "The fact that we had another way of interacting with [the host] with PowerShell" made it an easier transition, he said.
Another stumbling block is third-party software support. With ESX, backup and monitoring software vendors typically wrote agents that could be installed in the service console, not all of which have been updated to take advantage of ESXi's application programming interface (API) model -- or customers haven't yet upgraded to the latest version.
VMware argues that monitoring and backup software vendors have made strides in updating their wares to support these new APIs. "We've been working hard with our partners to migrate to the API-based integration model, as opposed to agent based," according to Jaleh Rezaei, the product marketing manager at VMware. "So when a customer comes to us and says, 'My software isn't supported,' often they find that the latest version does in fact support ESXi." Any software certified under the VMware Ready logo by definition supports ESXi, she said.
Regardless, there are ways to work around the need for third-party software agents, said vinternals' Radnidge, particularly monitoring agents: increase your use of VMware vCenter.
"Rather than load Common Information Model providers in there, you get the hardware status info from vCenter, and set alerts on that. Those get written to the log files, and the regular log file monitoring software picks them up," Radnidge said.
ESXi management benefits
ESX is entrenched in existing VMware shops, but there are pockets of ESXi adoption among forward-thinking enterprises and new installations.
"People that have never done anything with VMware are all going with ESXi," said Singler. "Unless they need special hardware monitoring or have existing scripts, there's no reason not to go with it."
Enterprise ESXi shops say the lightweight hypervisor offers many advantages over the full-blown version. In terms of security, ESXi's smaller footprint and lack of Linux service console makes it harder for hackers to tamper with or for administrators to make mistakes on.
That was the rationale for adoption by cloud computing provider Tier 3 in Seattle, Wash., according to Jared Wray, founder and CEO. "We were on the full-blown version of ESX 3.5, but with vSphere we moved to ESXi," said Wray. "It's this beautiful, small install [that's] all focused on VMware with no Red Hat or Linux to worry about."
Equally important is management simplicity. At vinternals.com, Radnidge said his firm standardized on ESXi as it migrated from Virtual Infrastructure 3.5 to vSphere 4.
"It's just a much simpler operational model," Radnidge said. The firm has in the neighborhood of 2,000 server VMs and 8,000 virtual desktops running on about 500 physical VMware hosts.
For instance, in ESX 3.5, "We treated the console like a full Linux OS, and stuck a lot of agents in there. Then we'd have problems with the agents when it came time to upgrade, which we don't have now," Radnidge said.
And because ESXi is delivered as "one monolithic binary image," patching an ESXi host is much simpler too, he said. "You don't have to worry about patch dependencies, install orders, or discrete pieces of software like a backup agent."
Further, because of its small size, ESXi can be installed on USB flash drives or secure digital SD cards within diskless servers, for improved power and cooling efficiency, said VMware's Bogomil Balkansky, the vice president of product marketing. .
ESX writing on the wall
Migrating to ESXi may seem like an onerous task, but ESX shops should start looking in that direction, said Chris Wolf, a senior analyst at Burton Group.
"VMware's made no secret of the fact that the ESX console is going to be end-of-lifed," Wolf said. So while it's still there in vSphere 4, "I'd be surprised if it was still there in version 5. Customers are going to have to plan on that in the next 24 to 36 months." Part of that planning process is to select management tools that already support ESXi.
VMware has thus far declined to say when it plans to stop providing new versions of ESX. "We have made no secret of the fact that ESXi is the preferred and better architecture, and we are encouraging customers to take a closer look at it," said VMware's Balkansky.
"On the other hand," he added, "we are very much aware that we have 150,000 customers, and the lion's share of them is on ESX. We aren't going to do anything to put customers in a tight spot."