MongoDB: Disk I/O % utilization on Data Partition has gone

Question

Last time I get alert from MongoDB Atlas:

Disk I/O % utilization on Data Partition has gone above 70 on nvme2n1 

But I have no any ideas how can I localize / query / index / part of code / problematic collection.

In what way can I perform any analyze to find out problem root-cause?

Answer 1

Not answer, but just seen that many people faced with similar problem. In My case root cause was: we had collection with huge documents that contain array of data (in fact - list of coordinates with some metadata), and update it as many times, as coordinates we have (when adding new coordinates). + some additional operations.

As I know MongoDB cannot fetch just part of document, it fetch full document, and when we fetch many different and big documents, they are not fit into MongoDB in-memory cache, and each time access into hard disc, that lead to this issue. So, we just split up this document on several, and this fixed issue. While we need frequent access to update/add this data, we keep it into different documents, and finally, after process done, we gather back all this documents into one big document, for "history check" purpose.