Why is CPU high when FabricPool is enabled?
Applies to
- ONTAP 9
- FabricPool/Cloud Tiering enabled systems
Answer
- Tiering scanners use most of the available background CPU cycles.
- These are actually the same as spare CPU cycles, but being used to ensure data is tiered off effectively.
- This is normal and should not be used to consider high CPU utilization.
- ONTAP 9.11.1 increases CPU due to an increase in number of scanners and increase in priority.
- ONTAP 9.12.1 introduces extra redirect scanners in
wafl scan status
output as a fix for CONTAP-75534.- More details in RFE CONTAP-353908.
- ONTAP 9.14.1 increases tiering scanners from 10 to 20 as documented in CONTAP-64247 for all systems, not just AFF.
Additional Information
- You can check the additional CPU load from all FabricPool WAFL scanners using wafltop.
- Example: Use the node shell command in
wafltop
collectionwafltop show -v cpu -i 10 -n 10
.
- Example: Use the node shell command in
- Slow tiering during high workload
- How to check for background CPU utilization in ONTAP 9