[mrtg] Re: Graphing lots of ports

Steve Shipway s.shipway at auckland.ac.nz
Tue Dec 7 02:14:49 MET 2004

>I have a pair of Linux machines graphing a lot of switch ports 
>(~35000 ports across 1500 devices each) on 5-minute intervals. 
>Disk I/O seems to be my biggest problem. The CPU load tends to 
We have a similar problem.  I find these help:
1) FAST DISKS. Get the fastest disk IO you can.  Nice quick SCSIs or SAN.
IDE just doesn't cut it.
2) Mount the filesystem with noatime option.  This speeds it up a lot as the
atime flag doesn't have to be updated.
3) Splt RRDs into multiple filesystems.  A big directory is a timewaster.
This is less significant, though.
4) Lots of memory.  UNIX will use all spare memory for disk cache.
5) Use RRDTool, not log files!  Of course, you are doing this already.
6) Tune the filesystem for smaller files and small block IO. You never need
more than the size of an RRD to be loaded, but you want it to block-load the
whole RRD file.

Hope this helps,


Steve Shipway: ITSS, University of Auckland
Email: s.shipway at auckland.ac.nz  Web: http://www.steveshipway.org/  
** We can only discover new oceans when we have the **
** courage to lose sight of the shore.              **

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