Collection Server
From FaHWiki
The Collection Server is used as a backup host to receive Work Units (WU) in the case the Work Server is unable to handle the uploaded WU. Its IP address is recorded in each WU index of the queue.dat file, and the server is listed on the Folding@Home server status webpage.
The Collection Server was originally introduced with version 5 of the Folding@home client. This made it possible to return completed results to an alternate host so that the client doesn't risk passing the Final Deadline of a WU and subsequently deleting that WU. 171.65.103.100 is the first Collection Server, and is still the back up for most work servers. 171.64.122.76 was added as a second Collection Server shortly after the release of the SMP client in early 2007 to share some of the workload. 171.64.122.86 was added as a third Collection Server in early 2008.
For security reasons the Collection Server will only accept results from WUs it knows have been assigned. The Work Servers normally publish lists of their assigned WUs to the Collection Server, but on occasion this does not occur. If in this circumstance the Work Server then becomes unavailable, the Collection server will refuse to accept WUs that were assigned by that Work Server subsequent to the last list being published, because it cannot guarantee that they have been genuinely assigned.
This refusal will be logged in FAHlog.txt with a message like the one below:
[07:47:54] - Server does not have record of this unit. Will try again later. [07:47:54] Could not transmit unit 06 to Collection server; keeping in queue.
The list for the Collection Server will be updated again when the Work Server is on-line again and then the WU will upload to either one.
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