# arc_summary
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ZFS Subsystem Report Fri Feb 11 11:32:07 2022
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Linux 5.4.0-89-generic 0.8.3-1ubuntu12.12
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Machine: loki (x86_64) 0.8.3-1ubuntu12.12ARC status: HEALTHY
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Memory throttle count: 0ARC size (current): 100.1 % 64.0 GiB
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Target size (adaptive): 100.0 % 64.0 GiB
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Min size (hard limit): 4.6 % 3.0 GiB
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Max size (high water): 21:1 64.0 GiB
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Most Frequently Used (MFU) cache size: 96.3 % 47.7 GiB
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Most Recently Used (MRU) cache size: 3.7 % 1.8 GiB
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Metadata cache size (hard limit): 75.0 % 48.0 GiB
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Metadata cache size (current): 44.8 % 21.5 GiB
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Dnode cache size (hard limit): 10.0 % 4.8 GiB
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Dnode cache size (current): 143.5 % 6.9 GiBARC hash breakdown:
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Elements max: 20.9M
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Elements current: 84.9 % 17.7M
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Collisions: 1.7G
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Chain max: 12
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Chains: 4.8MARC misc:
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Deleted: 3.2G
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Mutex misses: 485.7k
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Eviction skips: 248.0MARC total accesses (hits + misses): 19.1G
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Cache hit ratio: 84.6 % 16.1G
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Cache miss ratio: 15.4 % 2.9G
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Actual hit ratio (MFU + MRU hits): 83.7 % 16.0G
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Data demand efficiency: 93.2 % 7.5G
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Data prefetch efficiency: 11.0 % 2.6GCache hits by cache type:
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Most frequently used (MFU): 60.7 % 9.8G
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Most recently used (MRU): 38.2 % 6.2G
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Most frequently used (MFU) ghost: 0.2 % 26.5M
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Most recently used (MRU) ghost: 0.7 % 116.9M
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Anonymously used: 0.2 % 37.2MCache hits by data type:
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Demand data: 43.4 % 7.0G
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Demand prefetch data: 1.7 % 280.0M
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Demand metadata: 53.7 % 8.7G
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Demand prefetch metadata: 1.2 % 199.0MCache misses by data type:
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Demand data: 17.3 % 506.5M
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Demand prefetch data: 77.6 % 2.3G
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Demand metadata: 1.8 % 51.6M
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Demand prefetch metadata: 3.3 % 97.9MDMU prefetch efficiency: 4.7G
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Hit ratio: 41.9 % 2.0G
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Miss ratio: 58.1 % 2.8GL2ARC status: HEALTHY
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Low memory aborts: 3.9k
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Free on write: 618
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R/W clashes: 0
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Bad checksums: 0
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I/O errors: 0L2ARC size (adaptive): 385.6 GiB
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Compressed: 19.4 % 74.7 GiB
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Header size: 0.3 % 1.1 GiBL2ARC breakdown: 2.9G
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Hit ratio: 1.7 % 49.3M
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Miss ratio: 98.3 % 2.9G
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Feeds: 8.6ML2ARC writes:
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Writes sent: 100 % 2.0 MiBL2ARC evicts:
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Lock retries: 0
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Upon reading: 0
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Data is not exposed vi snmp so this would need a unix agent modification to identify and pull out requisite data. As Adam Sarkozi above indicated a bare minimum would be health status. But to be able to track arc stats and other metrics pulled from /sys/modules/zfs/parameters.
Top of my head some items would be:
l2arc size
l2arc low memory aborts
arc size (relation to 'c' total size)
arc hits
arc misses
demand hits
demand miss
prefetch hits
prefetch miss
basically the stats you can get from arc_summary but something that can be recorded/graphed over time.
# arc_summary
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