This Knowledgebase article describes an expected behavior with Neverfail Heartbeat
To view the results of the tests Neverfail carried out to discover the effects of having many thousands of files in a single folder, download manyfiles.zip and extract it to a suitable location.
The effects can very depending on the names format, number of files in the folder and whether or not 8.3-name creation is enabled.
Note: Users with very large folders may or may not see this effect depending on the shape of the names in the folder. If they do have the problem, it will affect the time taken to synchronize the large folder.
Summary of testing
In order to check if there are any effects of having large numbers of files in a folder, Neverfail performed the following tests: For example, was disabling the 8.3 name generation sufficient to guarantee fast synchronization of a large folder? Neverfail created 500,000 files with short names (Fxxxx) in 1 folder. Each file was 512 bytes long. Neverfail then made that folder the only protected folder and started a full system check. Because the files were so small there would have been no verify and they would have been immediately synchronized.
Time to create the files was 1hr 45mins.
Time for full system check was 1hr 39mins.
There was no noticeable overhead in synchronizing these files compared to creating them - the reading of the files on the active server and sending of the data was overlapped with the file creation on the passive server.