Odd SNMP behaviour when monitoring Win servers

[kayjay]

I recently upgraded from 1.8.8 to 2.2.5 and am struggling to understand strange SNMP behaviour when monitoring Windows servers that used to work OK on the old version.

1. The Windows servers run on VM's and may have 1~4 CPUs assigned.
2. My test example has CPU 2 and 3 assigned.
3. I use SNMP to get the CPU load values from the HOST-RESOURCES-MIB
4. I put CPU 2 & 3 into monitoring as individual items and all is OK
5. If I then put CPU 4 into monitoring then all 3 become unsupported:

See these errors:
cpu2.load" became not supported: SNMP error: (noSuchName) There is no such variable name in this MIB.
cpu3.load" became not supported: SNMP error: (noSuchName) There is no such variable name in this MIB
cpu4.load" became not supported: SNMP error: (noSuchName) There is no such variable name in this MIB

If I delete CPU 4 then the original CPU 2 & 3 become supported again. Can anyone explain why one unsupported stops all them. This is driving me crazy.


Thanks guys

[kayjay]

After further investigation I can see the cause. It is due to the bulk processing feature introduced in '2.2.3'.

Previously each item was queried separately which works OK for me but now all items are queried in one SNMPget using variable bindings. If any of the items are not supported then the SNMP response fails with the 'noSuchName' error and no values are returned.

This new feature is excellent and does improve performance a lot but in cases like this is there a way to force separate queries for each item like it used to, in a selective way?

These hosts run on a VM and each time the VM starts CPU's are assigned 'n' CPU's from a pool (up to 8 CPU's) so every time it runs the CPU's can be a assigned different group of CPU's. This means I never know what CPU's are in use. In 1.8.8 it worked great but now in this instance it is broken from 2.2.3 on.

Any ideas?

[ingus.vilnis]

Hi,

You could give a try for the latest Zabbix 2.4 where there is an option to disable SNMP bulk requests for devises that does not support that.

https://www.zabbix.com/documentation/2.4/manual/introduction/whatsnew240#optional_snmp_bulk_requests

Best Regards,
Ingus

[kayjay]

Ah! I thought I was going crazy

It has taken me two months to upgrade the production system from 1.8.8 to 2.2.5 (the latest at that time) on new higher performance hardware. I would like to upgrade but there are some unanswered questions, mainly concerning any changes that there may have been to the db structure. I now partition the db to stop the problem with db size of history tables and I cannot see if I can upgrade safely without breaking this.

Thanks

[ingus.vilnis]

There are some changes in DB structure but not in history tables - history, trends and events are unchanged from 2.2 to 2.4 so it is considered safe for you to upgrade even if using partitioning.

However don't forget to backup before upgrade anyways.

Best Regards,
Ingus

[kayjay]

Good news then

I assume that the db gets updated automatically when the server runs for the first time?

Thanks

[ingus.vilnis]

Yes, it does

Best Regards,
Ingus