I have a mongodb 2.6 replica set (1 primary and 1Secondary). I would like to upgrade to latest stable version 4.4. Do I need to follow the migration path i.e 2.6.11 → 3.0.15 → 3.2.22 → 3.4.24 → 3.6.18 → 4.0.18 → 4.2.6->4.4 or is there any way to directly upgrade to 4.4 with no or minimum downtime?
This is the recommended upgrade path.
Nothing that I have seen. Perhaps you can export and import, but you will want to perform adequate testing. The version to version upgrade path is well documented and tried and tested.
As stated in other similar threads, the amount of technical debt here will also apply to your clients/drivers. They will require a similar amount of attention.
This is essentially the same question as Replace mongodb binaries all at once? but with a different starting version (2.6 instead of 3.2).
The options I’ve outlined in that discussion apply to MongoDB 2.6 as well.
MongoDB 2.6 is below the minimum version for Cloud Manager Automation, but still supported by MongoDB Atlas Live Migration if you wanted to take that approach.
Since you are aiming for no or minimal downtime, you will have to manually upgrade through successive major versions (following the documented Upgrade Procedures) or use compatible automation tooling.