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Kode Vicious

System Administration

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Originally published in Queue vol. 15, no. 2
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(newest first)

Daniel Feenberg | Wed, 17 May 2017 13:32:55 UTC

The resource I see most often overused by monitoring systems isn't CPU but email and paging. Over-enthusiastic monitoring provides a deluge of uninformative alerts.

Is it a problem that 100% of the CPU or WAN link is in use? It is if there are a 100 users waiting on the resource, but in my shop it is typically a single user (even system houskeeping), and if another user came along they could get 50%. So no real problem, but I get alerts.

If the WAN link is down does the external monitor have to send a separate alert for every service on every system? Is there any point to waking everyone up when only one person (and not any of our staff at that) can fix the problem?

Yes, I know all these can be configured away and we have mostly done so. But it does take work and the reconfigured system will miss some perfectly valid problems. For instance, I would like to know if the WAN link is so overloaded that individual users are getting less than X throughput.

On the other hand, some monitoring is less strict than it should be. Pinging the mail server isn't much evidence that it is up. Looking for a sendmail banner is a bit better. Sending a message would be good, checking that it was received would be very good and checking that virus scanning and spam detection were actually working would be ideal.

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