1. If cloning a VM to a template takes a long time, usually, it is because that volume copy takes a long time during the cloning process. Therefore, we should first analyze the time cost for volume copy. After logging in to the VRM database, we found that it takes 7 hours to copy a 20 GB volume.
2. Therefore, we concluded that the problem was caused by slow volume copy speed.
3. After logging in to the related host, we found that data read speed of the data store containing the volume is 1.1 MB/s.
4. When checking the multi-path configuration, we found that four paths had been configured for the storage device.
5. After checking the read speed of the paths, we found that data read speed of three paths were slow.
6. After checking the storage device, we concluded that exceptions occurred on the cables connected to the storage devices or the interface cards of the storage devices. After we logged in to the storage device, an alarm was detected, indicating that the negotiation rate on the iSCSI port of the host was slow.
7. After checking the storage ports, we found that the speeds at the storage ports were similar to those of the paths.
8. Three of the four ports on the storage device worked at low speed. Therefore, the possible cause was that the cable connecting the host and the storage device was faulty.