At the place I work, we experienced continuous “The ramdisk ‘root’ is full” issues on our vSAN ESXi nodes.

The first thing we did was to raise a support call and have vmware check what is filling up the ramdisk.

Support suggested that we need to limit the size of vsantraces to 200MB, and pointed to the below KB Article

https://kb.vmware.com/kb/2150320

This puzzled me, as the vsantraces was not full.

Ramdisk Size Used Available Use% Mounted on
root 32M 32M 0B 100% --
etc 28M 5M 22M 18% --
opt 32M 368K 31M 1% --
var 48M 728K 47M 1% --
tmp 256M 492K 255M 0% --
iofilters 32M 0B 32M 0% --
hostdstats 1553M 17M 1535M 1% --
snmptraps 1M 0B 1M 0% --
vsantraces 300M 167M 132M 55% --

I kept digging and I found out that the scratch partition on the hosts was not pointing scratch -> /tmp/scratch

but it was on / instead.