I believe that journaling is enabled as we are currently taking regular scheduled snapshots.
I was asking more in general if it is still possible to take snapshots if one has used db.fsyncLock() .
The reason that I was thinking of doing this is to guarantee that the snapshot taken is exactly the same state as the database was before fsyncLock was used and so that no more writes to the database could be performed during the upgrade.
The situation I am trying to mitigate against is if something goes wrong during the upgrade, I want the snapshot that we recover the database from to be in the same state as before we started the upgrade.