I had a discussion yesterday about why one would care about changing the “OS” type for a VM when it is upgraded, or even during the provisioning of a VM. I guess the obvious one is that a VM is “customized / optimized” based on this information from a hardware perspective. Another one that many people don’t realize is that [...]

For those who hadn’t seen it yet, the “vSphere 4.1 HA/DRS Deepdive” is available in the Kindle Lending Library! The Kindle Owners’ Lending Library is a collection of books that Amazon Prime members who own a kindle can borrow once a month, with no due dates. (Yes you will need a Kindle Prime subscription!) If you have a Kindle or are [...]

As multiple people asked for it, Frank and I decided to also put the 4.1 HA/DRS Deepdive on sale. Just wanted to inform you guys about it. Here are the links: US – ebook – vSphere 4.1 HA/DRS Deepdive – $ 4.99 UK - ebook – vSphere 4.1 HA/DRS Deepdive – £ 3.99 FR - ebook – vSphere 4.1 HA/DRS Deepdive – [...]

I started digging in to this yesterday when I had a comment on my Metro Cluster article. I found it very challenging to get through the vSphere Metro Storage Cluster HCL details and decided to write an article about it which might help you as well when designing or implementing a solution like this. First things first, here are the [...]

On twitter Mike Laverick asked a question around DRS Affinity Rules and if HA would respect these. In this particular instance the question was around VM-Host affinity rules and I noticed multiple tweeps responding and figured it would not hut to repeat this. There are two different types of VM-Host affinity rules: Must aka mandatory Should aka preferential The difference [...]

I had a question this week from one of my colleagues which had me dazzled for a while. A customer had an HA enabled cluster and used “Host Failures Cluster Tolerates” as the admission control policy. As you hopefully all know it uses a slot algorithm, in short: HA uses the highest CPU reservation of any given VM and the [...]

There has been a lot of discussion in the past around Disk.SchedNumReqOutstanding and what the value should be and how it relates to the Queue Depth. Jason Boche wrote a whole article about when Disk.SchedNumReqOutstanding (DSNRO) is used and when not and I guess I would explain it as follows: When two or more virtual machines are issuing I/Os to [...]