We have in environment deployed some really small DBs (5GB) as directory per DB. Under dirs is LVM with XFS, where we have implemented logic for "brake" when DB space should be full-filled (all is due to some strict disk quotas - not really interesting at all I think...). Our solution runs on MongoDB v3.4.19 on CentOS 7.5. Everything looks ok.

Some of DBs has more than 60% used disk space by single collection and in our scenario we encountered that, while restoring 2.3GB dump (all into 5GB database dir/=disk, the preallocation after 2GBs asks OS for another space in (I think) power of 2 strategy (or something very similar).

This situation hits ours triggers, and eventually should lead to lock of DB (which is still better than fall of whole cluster because of no space left). Basically same situation we have with 10GB DB. (And in some way we can say that similar situation can occur with literally any capacity...)

My point of question is: Am I able to influence steps (maximum size lower than ~2GB) of (pre)allocation growing of Mongo/WT for restoring (only) or at all? **(As I've found that 2GB should be the max. value of growing up...)

Performance impact is not highest prioritized in this case.

The same I've asked on DBA StackExchange, but no solution found yet... (question [here|https://dba.stackexchange.com/questions/234301/how-to-influence-files-preallocation-steps-max-growing-value-in-mongodb-3-4])

If some additional info needed, let me know, please. Any hint/tip would be really appreciated...

Best regards

Zdenek.