not really docs but it is scattered around on the forums mostly

3 servers minimum, you can scale from there easily (just copy files as usual)

so, first, you'll want to set process classes (class = under [fdbserver.PORT] block)

there are only 3 that matter at small scales: storage, transaction, and stateless

storage handles data storage and you should give each storage server 8GB (if using ssd-redwood-1) or 4GB (ssd-2), and for best performance put 2 storage processes per disk

transaction handles transaction logs, you would ideally want dedicated disks for this but it can be shared with storage at small scale, but you should put only 1 transaction process per disk. you can use tiny disks and/or dedicated hosts for this

you can have as many stateless processes as you want per host but you would want at least 2 per server, and all that these need is good network/CPU