Go to Main Menu > Resource Monitor > Performance > CPU to check the utilization distribution.[8] If the utilization mainly consists of User, go to Task Manager > Services on the left panel to check which service or process is taking up more resources.[8]
A few notes from the knowledge base:
- Resource Monitor can show overall CPU usage and the CPU usage of each process in decreasing order of CPU load.[1]
- CPU load may be high right after launching Resource Monitor because the system needs to collect resource data and load the UI page at the same time.[1]
- Keeping Resource Monitor launched will consume system resources.[1]
- Memory usage can stay high because DSM keeps frequently accessed data in cache; this cache is released when overall memory becomes insufficient.[1]
To reduce load, the knowledge base suggests checking for common CPU-heavy services and processes in Resource Monitor and then following the related guidance, for example:
- SMB > smbd: if the SMB service network port (default 445) is open to external access, disable it; if it is only open internally, check whether it is being accessed normally by internal users.[8]
- Surveillance Station > sscamerad: if motion detection is set to By Surveillance Station, change it to By camera or Disable in Surveillance Station > IP Camera.[8]
If DSM UI navigation itself is slow, the knowledge base also points you to review:
1. high CPU utilization causes,
2. high volume utilization causes,
3. file system errors if applicable.[10]
If you are seeing high CPU during an update window, check recent CPU history in Resource Monitor > Performance > CPU, and also review Resource Monitor > Task Manager for background tasks such as data scrubbing, data deduplication, or space reclamation.[12]
Sources used: [1], [8], [10], [12]