understand bonnie++ output

[henryz17]

Chart with different outputs. Plutus has no slog

[henryz17]

`[root@plutus ~]# arc_summary -s arc

---

ZFS Subsystem Report Fri Oct 07 15:15:33 2022
Linux 4.18.0-372.16.1.el8_6.0.1.x86_64 2.1.5-2
Machine: plutus.atmos.ucla.edu (x86_64) 2.1.5-2

ARC status: HEALTHY
Memory throttle count: 0

ARC size (current): 47.8 % 30.0 GiB
Target size (adaptive): 100.0 % 62.7 GiB
Min size (hard limit): 6.2 % 3.9 GiB
Max size (high water): 16:1 62.7 GiB
Most Frequently Used (MFU) cache size: 20.0 % 6.0 GiB
Most Recently Used (MRU) cache size: 80.0 % 23.9 GiB
Metadata cache size (hard limit): 75.0 % 47.0 GiB
Metadata cache size (current): 0.2 % 112.0 MiB
Dnode cache size (hard limit): 10.0 % 4.7 GiB
Dnode cache size (current): < 0.1 % 1.2 MiB

ARC hash breakdown:
Elements max: 2.1M
Elements current: 14.5 % 297.6k
Collisions: 441.4k
Chain max: 4
Chains: 2.6k

ARC misc:
Deleted: 1.7M
Mutex misses: 78
Eviction skips: 0
Eviction skips due to L2 writes: 0
L2 cached evictions: 0 Bytes
L2 eligible evictions: 210.9 GiB
L2 eligible MFU evictions: 0.2 % 373.1 MiB
L2 eligible MRU evictions: 99.8 % 210.5 GiB
L2 ineligible evictions: 384.0 KiB`

[henryz17]

graph for zpool on argo with and without slog. metadata latency is where we see the most significant difference.