Cron Auto-Archiving timeout issue. (no replies)

Hi,

We use PIWIK since 2010. We have now about 10 websites with about 20 000-30 000 connections per days (not all of them are track by piwik maybe only 2 000 or less).
We have some performance issue, so i would like to use cron for auto archiving instead of 'Browser trigger archiving'.
In the documentation it's says : "Generally, it completes in less than one minute"

So i tried and here is the log :

INFO CoreConsole[2014-09-18 14:07:24] [0a486] - Reports for today will be processed at most every 10 seconds. You can change this value in Piwik UI > Settings > General Settings.
INFO CoreConsole[2014-09-18 14:07:24] [0a486] - Reports for the current week/month/year will be refreshed at most every 3600 seconds.
INFO CoreConsole[2014-09-18 14:07:24] [0a486] - Will process 8 websites with new visits since 7 jours 0 heures , IDs: 1, 2, 3, 6, 8, 9, 10, 14
INFO CoreConsole[2014-09-18 14:07:24] [0a486] Will ignore websites and help finish a previous started queue instead. IDs: 3, 12
INFO CoreConsole[2014-09-18 14:07:24] [0a486] ---------------------------
INFO CoreConsole[2014-09-18 14:07:24] [0a486] START
INFO CoreConsole[2014-09-18 14:07:24] [0a486] Starting Piwik reports archiving...
INFO CoreConsole[2014-09-18 14:07:39] [0a486] Archived website id = 3, period = day, 29 visits in last last52 days, 0 visits today, Time elapsed: 14.967s
INFO CoreConsole[2014-09-18 14:11:28] [0a486] Archived website id = 3, period = week, 297 visits in last last260 weeks, 1 visits this week, Time elapsed: 229.423s
ERROR CoreConsole[2014-09-18 14:11:28] [0a486] SQLSTATE[HY000]: General error: 2006 MySQL server has gone away

How can i avoid MYSQL timemout ? I thinks my mysql timeout is enought.(2 min)