mongodb - Why is my mongo migration with Wired Tiger 10x slower than MMAP? -


i have pretty simple data migration, we're splitting embedded documents out of 1 collection own collection. have 140,000 records create.

in testing on local mongo 3.4 mmapv1 migration took 20 minutes run.

in production, migration took on 4 hours run!

i did experiments, switched local storage wt , imported data , ran migration again, took 4 hours, difference being wt storage configuration (with defaults including snappy compression).

loading initial dataset fast mmap or wt, suspect compression not issue, curious if knows why such drastically different result between 2 data storage mechanisms


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