Ever wonder what block sizes your VM’s are using for writing and reading to disk? I always have and I recently found a way to get this information out of the ESXi hypervisor. You can also get a lot of other data such as random and sequential writes, latency, and a few other items.
- Connect to the host with SSH.
- Enter the command “vsciStats -l” This will list all the VM’s on that host and its disk.
- vsciStats -s will start that stats collection. You can pair this down by using the -w for the world group id and -i for handle id.
- vsciStats -p ioLength -w 123456 would display the block sizes for that particular VM and drives.
- -h will give you a list of all the possible variables to use.