[mrtg] Intermittent Graphs

[Steve Shipway]

I found that the biggest bottleneck is not CPU, but disk IO speed.  Therefore, abosolutely the fasted disks (multiple spindles in a RAID if possible) and the highest speed interfaces - Fibre, SAS, or SCSI, definitely not IDE.  This stops the bottleneck. The next problem is to have enough memory to hold the queries.
 
Next, I run multiple threads of MRTG (since there are 4 CPUs I can have at least 4 threads at once) and spread these over the 5-min window so that it doesnt all happen at the same time (I have a home-grown script that takes care of this scheduling).  This allows me to have 4000+ targets on a 4x3GHz CPU box with 4Gb memory and 4 disks in a SAS-attached RAID, and still have lots of free memory and about 70% CPU use.  The disk IO is almost saturated, though.
 
Steve
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