Virtualization Pro

Jul 23 2008   8:48PM GMT

Performance tips from the summer New England VMUG; attendees sound off

HannahDrake Hannah Drake Profile: HannahDrake

425 IT geeks invaded Brunswick, Maine last Thursday for the New England VMware Users Group summer meeting at Brunswick High School. The event, which started at 10 AM with a sponsor showcase and proceeded with after-lunch sessions, concluded in a Lobster/Clambake at Gritty’s in Freeport, Maine.

Mike Burke, Virtual Infrastructure Practice Director, VIRTERA

 “Good performance starts with proper planning and design, configuration best practices and operational awareness,” said Mike Burke (left), Virtual Infrastructure Practice Director for Virtera, a CT-based consulting firm during the first session I attended equivocally titled “Getting the most out of your ESX Environment – Performance tuning.”

“Tuning is not a replacement for proper planning and design,” Burke said. “Don’t guess; gather the data.”

Planning trumps tuning in VMware deployments
Performance, Burke said, hinges on examining and understanding how CPU, memory, networking and disk space will work together in a virtual infrastructure. Planning, then, is the key to better ESX performance, and not necessarily tuning.

Generally speaking, more cores are better; so plan on going big. “How does VMware license their product? Per socket. If you can choose a quad-core, it’s a lot more economical,” Burke said, citing that AMD series processors are now “dirt cheap” compared to earlier years, with eight core boxes going for around $2000.

“You need to weigh what the workload is against what the goals of virtualizing it are,” Burke said. For example, a four-CPU physical server may not be a good candidate for a server consolidation project if it’s currently using the four CPUs to the fullest extent, because you won’t have a good consolidation ratio on those systems. It may, however, be a candidate if the goal is overall server virtualization instead of consolidation.

Another reason for this type virtualization is hardware capability. You can’t VMotion from AMD to Intel. Even in servers from the same line, Burke said, older hardware instruction sets coded in the CPU won’t look the same, preventing VMotion capability.

More host RAM gives better overall performance, configure a VM’s memory based on actual need – are you really using the full two GHz, or would it better used elsewhere? On a general note, though, Burke said “oversubscribing,” or provisioning more memory for virtual machines in the physical host server, is better than not.

Advanced configurations
A systems administrator can, however, tweak a few advanced variables in a virtual machine’s configuration or vmx file. For memory, you can reset the time interval for transparent page sharing (TPS), which is automatically set at 60 seconds, by using mem.ShareScanTime. Adjust the memory pages to scan per 1 GHz idle cycle, automatically set at 4 MB/sec per 1GHz by using mem.ShareScanGhz. mem.CtlMaxPercent limits memory reclamation by ballooning.

But tweaking these parameters, Burke warned, can detract from virtualizing your systems. “You’re instructing ESX to spend more time processing and looking for memory savings rather than sitting in the background and running the VMs, which diverts resources away from virtualizing guests to handling these configurations on the backend.”

On a per-VM level, you can use the same mem.CtlMaxPercent command, and also: sched.mem.maxmemstl, which caps the max memory reclamation by ballooning (vmmemctl); sched.mem.pshare.enable – enables/disables memory sharing (TPS); lastly, using sched.swap.persist can enable vSwap to persist after power-off.

New England VMware Users Group summer meeting attendees sound off
Other sessions spanned from technical sessions about VMware DRS and HA to VDI demonstrations, SRM implementation and general topics, such as managing the virtual data center and how to minimize VM sprawl. Some sessions were led by speakers from consulting companies; others were 45 minute long vendor sales pitches disguised as learning sessions, but overall attendees had a good experience.

“For me, the sessions are good, but I can learn the same material in a textbook or on a website,” said Lee Pullen of the Maine Education Association. “The largest benefit is the networking, meeting other users and finding out what they’re doing in their own environments. That’s the real value in attending.”

“I found a few of the titles of the sessions misleading,” said State of Maine Office of Information Technology employee Lori Blier. “The last session I was at seemed like it was going to be about getting more out of your virtual infrastructure, which is what it was called. But they mainly talked about virtual desktops.”

Perhaps next year, the organizers could include descriptions of the presentations so that participants know exactly what to expect, Blier suggested. She said that she liked the sessions that discussed managing and using ESX Server, which is what the state of Maine plans to upgrade to pending management approval. They currently use VMware Server in production.

“I was a little disappointed that there were no sessions or vendors that focused on the networking side,” commented Kris Kirby from the Vermont Agency of Natural Resources, who said that’s his main concern with his VMware environment. “I also thought it was going to start a little earlier.”

Chris Harney, a systems engineer from Maine who organizes the New England Users Group meetings, said that feedback from the last session indicated increased interest in virtual desktop information sessions, which is why several of the sessions catered to that track. He also said that if networking came up as a trend on the feedback sheets, it would be voted on by a focus group and most likely included in the program for the January winter meeting, which will be held in Massachusetts.

“We’ve only been doing this for a couple years, and we’re still trying to figure out what works,” Harney said. “This is just a hobby for me, but it’s almost a full-time job. When we first started, we had 35 people. Now we’re looking at almost 500 per meeting.”

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