thanks again for your assistance johnnie.black
i followed your instructions exactly. iv highlighted the steps i performed.
after starting the array i get the unmounted message. im removing cache 2 i kept an eye on the writes count. they didnt change at all and the disk still says unmounted.
screenshot attached
[glow=green,2,300]backup your cache in case something unexpected happens
shutdown server
remove disk (disk has to be physically disconnected or precleared, starting the array with a previously used pool disk unassigned will result in unmountable cache)
power up, start array[/glow]
1) if disk removed was cache1: balance will begin, progress can be seen on cache webpage
2) if disk removed was cache2 and the only one left is cache1: balance will begin, no balance progress will be shown, wait for cache read/write activity to stop
this can take some time depending on how much data is on the pool and how fast your devices are, don't stop the array until it's done
when balance is done check that on the cache page "btrfs filesystem show" total devices are correct and it's not displaying "***some devices missing"
if you removed cache1 and plan to only keep using cache2 it’s ok to trade slots and assign it as cache1