I was always under the impression that ESX 3.x still used “strict co-scheduling” as 2.5.x did. In other words when you have a multi vcpu vm all vcpu’s need to be scheduled and started at the same time on seperate cores/cpu’s. You can imagine that this can cause the VM to have high “ready times”, which means waiting for physical [...]

Because I will be posting less in the upcoming weeks about problems I face at customer sites I will try to post some cool command-line tip or trick I discovered or picked up somewhere…. open ESX console ,via putty and type the following vm-support -x result: all the VMID’s also known as World ID’s, And if you’re colleagues hardly ever [...]

The common mis perception of the term “snapshot”, related to VMware, can cause huge problems. I’ve spend a lot of time the last years solving snapshot problems. For once and for all, a snapshot isn’t a static situation like a clone is. A snapshot can best be compared to a redo log, although technically it isn’t because it’s just a [...]

Just noticed the following topic, which definitely contains some good info about how ESX deals with memory. Thanks to Kit for clearing things up. These posts are valuable, keep ‘em coming! a short outtake: Basically how aggressive do you want TPS to scan for shared pages? Obviously TPS has a cost to running in terms of CPU, but has benefits [...]

At a customer site we noticed that the ESX hosts were swapping, Nagios generated a nice alarm. After some research it seemed like certain VM’s were swapping to the VMFS volume, so not inside the OS but VMware swap usage. A closer look at the system revealed that we weren’t overcommitting. There was over 6GB of memory free and there [...]

Yesterday evening I witnessed a weird phenomenon. We had to bring down a complete environment to move a 19″ rack to a different location. We switched the SAN on, waited a couple of minutes and switched the ESX hosts on. When the ESX hosts finished booting we booted the VirtualCenter. Everything looked normal in the VI Client. I had all [...]

Today a customer called about a problem with the Exchange VM. For some reason the ESX Host where this VM resided was always swapping/ballooning. They checked and double checked the settings but could not find the problem. After a quick scan I noticed that there were limits set on memory for each VM. This particular VM had 1536MB of memory [...]