I'm a user from china. First apologize for my poor english.
I use zabbix to monitor network devices, such as switches and routers. I found that many types of network device has a snmp thread limit (the limit cannot be modified). If snmp thread number exceed the limit, the device will break snmp connections for a while. This will cause zabbix cannot obtain item values in this period. "StartPollers=" in zabbix_server.conf is a global numbers of poller. But I can't define poller numbers for each host. Some other software, such as cacti, can define threads of each host. So I hope zabbix will add this feature in the future versions.
Thanks for your selfless dedication. Best regards to you.