Steps to reproduce:

1. Add vCenter host to zabbix via built-in template
2. Start monitoring huge production
3. See hundred of logs/unsupported items per day

Result:
  1671:20220726:125532.755 item "[id-id-id-id]:vmware.vm.vfs.dev.read[\{$VMWARE.URL},\{HOST.HOST},scsi0:11,ops]" became not supported: Timeout was reached

1674:20220726:125517.722 item "dc-vcenter:vmware.datastore.read[\{$VMWARE.URL},DS-01,latency]" became not supported: Counter datastore/totalReadLatency[average] for datastore DS-01 is not available for hypervisor hypervisor.corp: timeout was reached
(many times, many items)

Expected:

no timeouts or unsupported items

Problem occurred on 2 different environments virtual and physical zabbix server and different vcenter version. To reproduce problem you need to monitor ~2000 items, update interval is 1 minute.

It occurs periodically, and restored too:

  1671:20220726:134932.535 item "id-id-id-id:vmware.vm.cpu.ready[\{$VMWARE.URL},\{HOST.HOST}]" became supported

cat /var/log/zabbix/zabbix_server.log | grep vmware | grep -c 'became supported'
118938

config:

1. 1. 1. Option: StartVMwareCollectors
2.       Number of pre-forked vmware collector instances.
   #
3. Mandatory: no
4. Range: 0-250
5. Default:
   StartVMwareCollectors=8

1. 1. 1. Option: VMwareFrequency
2.       How often Zabbix will connect to VMware service to obtain a new data.
   #
3. Mandatory: no
4. Range: 10-86400
5. Default:
   VMwareFrequency=60

1. 1. 1. Option: VMwarePerfFrequency
2.       How often Zabbix will connect to VMware service to obtain performance data.
   #
3. Mandatory: no
4. Range: 10-86400
5. Default:
   VMwarePerfFrequency=60

1. 1. 1. Option: VMwareCacheSize
2.       Size of VMware cache, in bytes.
3.       Shared memory size for storing VMware data.
4.       Only used if VMware collectors are started.
   #
5. Mandatory: no
6. Range: 256K-2G
7. Default:
   VMwareCacheSize=32M

1. 1. 1. Option: VMwareTimeout
2.       Specifies how many seconds vmware collector waits for response from VMware service.
   #
3. Mandatory: no
4. Range: 1-300
5. Default:
   VMwareTimeout=300