So in my case I have 32872 Mhz and 40963MB of total capacity. My slot size is 32Mhz/80MB. Maximum number of CPU slots I can have is 328.25. Maximum number of RAM slots 40963/80=512.0375 which defines the number of total slots as HA chooses the most restrictive number (a worst case scenario). The slot size for Memory is the highest reservation of Memory among all VM’s in the cluster (or 0 MB + Memory Overhead if no per VM reservations exist). If you want to really dive further into HA and slot size calculations, I would highly recommend reading Duncan Epping’s HA Deepdive at Yellow-Bricks.com. A slot size takes into account the largest combination requirements of memory and CPU per VM. In this example you'll see that the current failover capacity is 1. So if the admin setup the failover capacity to 2, additional VMs can't be powered On. You can click to enlarge.
A previous post on my blog shows us how to get the slot size information for each cluster which has HA enabled, it also discusses what a slot size is and points to some further reading on Yellow-Bricks.
Readers of the great HA and DRS book will know exactly what a slot size is, if you are unsure then I suggest you read my previous article or the HA and DRS book, it is important information to know.
But which VMs are setting your slot size ? This is a question which was emailed to me over a year ago, someone had issues finding the VMs which were setting their slot size and they had run out – not a good place to be.
I wrote a script for them and asked them to test it, then I completely forgot about it – until recently when the question came up again.
Now you probably think you know which VM’s are setting your slot size but the thing that struck me is that nearly all the people I asked to check this came back with the same comments:
Yep, it works and wow, I had forgotten about that machine and the resources I allocated to it !
So please, download it and give it a go, who knows you too may have a surprise.
Sample Results
Video Walkthrough
Script
Make sure you change the connection details in the first line.
Vsphere Ha Slot Size
We recently moved our ISO store from a legacy NFS server to our main NFS filer.
The first task was copying the actual files, which can be done via any machine that has both datastores mounted (with read-write access to the destination store).
The more significant job is reconfiguring the VMs to use the copies of the ISOs in the new datastore.
Here’s the PowerCLI script I used:
Vsphere Slot Size
It’s fairly self-explanatory.
The biggest caveat with this is that it assumes that the source and destination stores have the same structure, but it wouldn’t be difficult to amend it to change the destination path slightly.