Arbiter dbpath size calculation in replica set

I have created replica set cluster of combination Primary/Secondary/Arbiter.
Mongo version: Mongo 3.6.9

For Primary/Secondary data members, have configured specific dbpath size based on our usage demand.
As Arbiter member does not store data, need suggestion what is ideal dbpath size to given. And i observe dbpath utilization keep growing over a period of time, though its in small MBs.

Since, i use dbpath from RAM(for faster access to data), don’t want to allocate more RAM to Arbiter member where there are no data operations except for voting. Please suggest in what is ideal dbpath size to be given for Arbiter members.


I cannot comment on the other subject but about:

I am not too sure it is a good idea. The storage engine are really good at caching the working sets in RAM. Giving RAM as “permanent” storage is making sure the storage engine has less RAM for the working sets. I do not have numbers to backup my claims but I would not opt for such a performance enhancement without real performance testing.

Thanks Steeve for your comments.
Our application needs real time response, it is very much required to use RAM for storage. And coming to performance, we use decent Sizing of RAM of around 64GB+ and it shows good results so far.