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CONTAP-770120: Node Panic Due to WAFL Very Low Memory State After ONTAP Upgrade

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Issue

After upgrading to ONTAP 9.18.1P5, a FAS2720 node experienced multiple panics and unresponsiveness due to WAFL running very low on memory. The following symptoms and log messages were observed:
Node1:free_cache_trigger_proc:wafl.memory.statusVeryLowMemory:alert]: WAFL is running very low on memory, with <500-550MB remaining
Node paniced and rebooted
Panic string: Process mgwd unresponsive for 746 seconds (mgwd startup: "(4019)") in process node watchdog on release 9.18.1P5(C)
Core dump generated for analysi and the issue was most pronounced on nodes hosting large aggregates with heavy workloads.
The system was found to have 1TB FlashCache NVMe modules installed and active.

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