Transfer returns 0 bytes free and reduces threads to 1

Symptoms

Transfer Tool returns the following error to cPanel's error_log file.

CONFIG_TEXT: "warn [start_transfer] Transfer threads reduced to “1”:
Insufficient disk space is available. “/home” on host “xx.xx.xx.xx” has 0 bytes
free and requires at least 68 KB free, which includes space for temporary files..

Threads are forced to 1.

Cause

During a transfer session, cPanel reads the filesystem info to determine if the source will fit on the destination server. This can be an essential aspect of migrating many accounts. Threads are forced to 1 if there is no disk space available to prevent the server from crashing under heavy load. 

However, in some instances, it is a false match because the filesystem info was never returned to the transfer tool session. This can occur if the source server previously transferred accounts from a much older version of cPanel.

We've opened an internal case for our development team to investigate this further. For reference, the case number is CPANEL-46059. Follow this article to receive an email notification when a solution is published in the product.

Resolution

Remove the analyze_config script on the source server to allow a new file to be downloaded automatically during the next transfer attempt.

# /bin/rm /usr/local/cpanel/scripts/analyze_config

After the file is removed, you should be good to go and initiate a new transfer.