Hi, We use Nagios on several servers, in version 2.9 with NDO 1.4b5 and perf2rdd (nagios write performance data in a pipe file and perf2rrd perform it in rrd file). Running on RHEL4 with package from <a href="http://dag.wieers.com"> dag.wieers.com</a> we have 80 hosts and 420 services on this server. We can see some huge gaps in our graphs, perf2rrd works fine, my first investigation shows this message in nagios.log file : [1193178252] ndomod: Error writing to data sink! Some output may get lost... [1193178268] ndomod: Successfully reconnected to data sink! 0 items lost, 240 queued items to flush. [1193178269] ndomod: Successfully flushed 240 queued items to data sink. [1193187298] Warning: A system time change of 8729 seconds (forwards in time) has been detected. Compensating... [1193190553] Warning: A system time change of 3255 seconds (forwards in time) has been detected. Compensating... we have recompiled nagios with debug mode : --enable-DEBUG2 shows warning messages --enable-DEBUG3 shows scheduled events we don't use le DEBUG0 because it generates too much informations and the log file increases too fast. so, I found this message in debug information, with the last gap : - Masquer le texte des messages précédents - *** Event Check Loop *** Current time: Wed Oct 24 00:29:29 2007 Next High Priority Event Time: Wed Oct 24 00:29:30 2007 Next Low Priority Event Time: Wed Oct 24 00:29:29 2007 Current/Max Outstanding Service Checks: 19/65 *** Event Details *** Event time: Wed Oct 24 00:29:29 2007 Event type: 0 (service check) Service Description: LOAD_AVERAGE@LOADAVERAGE Associated Host: SGBD1 Checking service 'LOAD_AVERAGE@LOADAVERAGE' on host 'SGBD1'... - Masquer le texte des messages précédents - *** Event Check Loop *** Current time: Wed Oct 24 00:29:29 2007 Next High Priority Event Time: Wed Oct 24 00:29:30 2007 Next Low Priority Event Time: Wed Oct 24 00:29:29 2007 Current/Max Outstanding Service Checks: 20/65 *** Event Details *** Event time: Wed Oct 24 00:29:29 2007 Event type: 0 (service check) Service Description: LOAD_AVERAGE@LOADAVERAGE Associated Host: INTEG Checking service 'LOAD_AVERAGE@LOADAVERAGE' on host 'INTEG'... Warning: A system time change of 8729 seconds (forwards in time) has been detected. Compensating... *** Event Check Loop *** Current time: Wed Oct 24 02:54:58 2007 Next High Priority Event Time: Wed Oct 24 02:54:59 2007 Next Low Priority Event Time: Wed Oct 24 02:54:58 2007 Current/Max Outstanding Service Checks: 21/65 *** Event Details *** Event time: Wed Oct 24 02:54:58 2007 Event type: 0 (service check) Service Description: MONITOR_TELNET_SUIVI_PS Associated Host: PREPROD1 Checking service 'MONITOR_TELNET_SUIVI_PS' on host 'PREPROD1'... Warning: A system time change of 3255 seconds (forwards in time) has been detected. Compensating... *** Event Check Loop *** Current time: Wed Oct 24 03:49:13 2007 Next High Priority Event Time: Wed Oct 24 03:49:14 2007 Next Low Priority Event Time: Wed Oct 24 03:49:13 2007 Current/Max Outstanding Service Checks: 22/65 *** Event Details *** Event time: Wed Oct 24 03:49:13 2007 Event type: 0 (service check) Service Description: MONITOR_TELNET_SUIVI_PS Associated Host: BIDS15 Checking service 'MONITOR_TELNET_SUIVI_PS' on host 'BIDS15'... we can see the jump 00:29:29 to 02:54:58 and 02:54:58 to 03:49:13 without activity in nagios! I dont understand this! if you can give me some help to have a nagios server with more stability. I dont know how to reproduce this bug. At the time a gap was accuring, the server time was up to date. We have on this server more than a gap by day! best regards, Olivier