Replication fetchLatestIndex always failed, that will occur the recovery error.

Usually the copy full index 70G need 20 minutes at least, 100M read/write network or disk r/w. If in the 20 minutes happen one hard commit, that means the copy full index snap pull will be failed, the temp folder will be removed because it is failed pull task.
In the production, update index will happen in every minute, redo pull task always failed because index always change.

And also always redo the pull it will occur the network and disk usage keep the high level.

For my suggestion, the fetchLatestIndex can be do again in some frequency. Don't need remove the tmp folder, and copy the largest index at first. Redo the fetchLatestIndex don't download the same biggest file again, only will copy the commit index just now, at last the task will be easy success.