在zfs ssd上使用带有50Gb文件的nginx proxy_cache的Debian服务器。 Arc max_arc_size设置为4Gb，但它总是大约200Mb。大约有15Mb / s的读数（~2000 iops）。
以下是弧形统计数据：
6 1 0x01 91 4368 4519739210 20260794068709869
name type data
hits 4 1091659308
misses 4 2527747210
demand_data_hits 4 199239091
demand_data_misses 4 879731305
demand_metadata_hits 4 878147163
demand_metadata_misses 4 1620108834
prefetch_data_hits 4 3576788
prefetch_data_misses 4 26135774
prefetch_metadata_hits 4 10696266
prefetch_metadata_misses 4 1771297
mru_hits 4 748623935
mru_ghost_hits 4 4693446
mfu_hits 4 329085083
mfu_ghost_hits 4 572404
deleted 4 3416733423
mutex_miss 4 2921118
evict_skip 4 1998987007908
evict_not_enough 4 65487161254
evict_l2_cached 4 8503750861312
evict_l2_eligible 4 53782247538176
evict_l2_ineligible 4 1007328996352
evict_l2_skip 4 123543938
hash_elements 4 547710
hash_elements_max 4 12455750
hash_collisions 4 4764403886
hash_chains 4 33097
hash_chain_max 4 17
p 4 2171871232
c 4 4294967296
c_min 4 1073741824
c_max 4 4294967296
size 4 197336056
hdr_size 4 2416376
data_size 4 19205120
metadata_size 4 88721920
other_size 4 30579920
anon_size 4 26062848
anon_evictable_data 4 0
anon_evictable_metadata 4 0
mru_size 4 80666112
mru_evictable_data 4 1671168
mru_evictable_metadata 4 4380160
mru_ghost_size 4 0
mru_ghost_evictable_data 4 0
mru_ghost_evictable_metadata 4 0
mfu_size 4 1198080
mfu_evictable_data 4 0
mfu_evictable_metadata 4 540672
mfu_ghost_size 4 0
mfu_ghost_evictable_data 4 0
mfu_ghost_evictable_metadata 4 0
l2_hits 4 375974103
l2_misses 4 2145995954
l2_feeds 4 20211060
l2_rw_clash 4 463
l2_read_bytes 4 6363894670336
l2_write_bytes 4 4125367876608
l2_writes_sent 4 15985006
l2_writes_done 4 15985006
l2_writes_error 4 0
l2_writes_lock_retry 4 14130
l2_evict_lock_retry 4 268
l2_evict_reading 4 1
l2_evict_l1cached 4 159
l2_free_on_write 4 1407463
l2_cdata_free_on_write 4 17
l2_abort_lowmem 4 36
l2_cksum_bad 4 0
l2_io_error 4 0
l2_size 4 14377400320
l2_asize 4 14376536576
l2_hdr_size 4 56412720
l2_compress_successes 4 1844601
l2_compress_zeros 4 0
l2_compress_failures 4 145
memory_throttle_count 4 0
duplicate_buffers 4 0
duplicate_buffers_size 4 0
duplicate_reads 4 0
memory_direct_count 4 1
memory_indirect_count 4 9
arc_no_grow 4 0
arc_tempreserve 4 0
arc_loaned_bytes 4 0
arc_prune 4 283684792692
arc_meta_used 4 178130936
arc_meta_limit 4 107374182
arc_meta_max 4 1415965680
arc_meta_min 4 16777216
arc_need_free 4 0
arc_sys_free 4 131072
以下是zfs参数：
l2arc_feed_again 1
l2arc_feed_min_ms 200
l2arc_feed_secs 1
l2arc_headroom 8
l2arc_headroom_boost 200
l2arc_nocompress 1
l2arc_noprefetch 0
l2arc_norw 0
l2arc_write_boost 8388608
l2arc_write_max 83886080
metaslab_aliquot 524288
metaslab_bias_enabled 1
metaslab_debug_load 0
metaslab_debug_unload 0
metaslab_fragmentation_factor_enabled 1
metaslab_lba_weighting_enabled 1
metaslab_preload_enabled 1
metaslabs_per_vdev 200
spa_asize_inflation 24
spa_config_path /etc/zfs/zpool.cache
spa_load_verify_data 1
spa_load_verify_maxinflight 10000
spa_load_verify_metadata 1
spa_slop_shift 5
zfetch_array_rd_sz 1048576
zfetch_block_cap 256
zfetch_max_streams 8
zfetch_min_sec_reap 2
zfs_admin_snapshot 0
zfs_arc_average_blocksize 8192
zfs_arc_grow_retry 1
zfs_arc_lotsfree_percent 10
zfs_arc_max 4294967296
zfs_arc_meta_adjust_restarts 4096
zfs_arc_meta_limit 0
zfs_arc_meta_min 0
zfs_arc_meta_prune 10000
zfs_arc_meta_strategy 1
zfs_arc_min 100
zfs_arc_min_prefetch_lifespan 0
zfs_arc_num_sublists_per_state 8
zfs_arc_p_aggressive_disable 1
zfs_arc_p_dampener_disable 1
zfs_arc_p_min_shift 4
zfs_arc_shrink_shift 5
zfs_arc_sys_free 131072
zfs_autoimport_disable 1
zfs_dbgmsg_enable 0
zfs_dbgmsg_maxsize 4194304
zfs_dbuf_state_index 0
zfs_deadman_enabled 1
zfs_deadman_synctime_ms 1000000
zfs_dedup_prefetch 0
zfs_delay_min_dirty_percent 60
zfs_delay_scale 500000
zfs_dirty_data_max 3370398924
zfs_dirty_data_max_max 8425997312
zfs_dirty_data_max_max_percent 25
zfs_dirty_data_max_percent 10
zfs_dirty_data_sync 67108864
zfs_disable_dup_eviction 0
zfs_expire_snapshot 300
zfs_flags 0
zfs_free_leak_on_eio 0
zfs_free_max_blocks 100000
zfs_free_min_time_ms 1000
zfs_immediate_write_sz 327680
zfs_max_recordsize 1048576
zfs_mdcomp_disable 0
zfs_metaslab_fragmentation_threshold 70
zfs_mg_fragmentation_threshold 85
zfs_mg_noalloc_threshold 0
zfs_nocacheflush 1
zfs_nopwrite_enabled 1
zfs_no_scrub_io 0
zfs_no_scrub_prefetch 0
zfs_pd_bytes_max 52428800
zfs_prefetch_disable 0
zfs_read_chunk_size 16384
zfs_read_history 0
zfs_read_history_hits 0
zfs_recover 0
zfs_resilver_delay 2
zfs_resilver_min_time_ms 3000
zfs_scan_idle 50
zfs_scan_min_time_ms 1000
zfs_scrub_delay 4
zfs_send_corrupt_data 0
zfs_sync_pass_deferred_free 2
zfs_sync_pass_dont_compress 5
zfs_sync_pass_rewrite 2
zfs_top_maxinflight 32
zfs_txg_history 0
zfs_txg_timeout 5
zfs_vdev_aggregation_limit 131072
zfs_vdev_async_read_max_active 3
zfs_vdev_async_read_min_active 1
zfs_vdev_async_write_active_max_dirty_percent 60
zfs_vdev_async_write_active_min_dirty_percent 30
zfs_vdev_async_write_max_active 10
zfs_vdev_async_write_min_active 1
zfs_vdev_cache_bshift 18
zfs_vdev_cache_max 16384
zfs_vdev_cache_size 0
zfs_vdev_max_active 1000
zfs_vdev_mirror_switch_us 10000
zfs_vdev_read_gap_limit 32768
zfs_vdev_scheduler noop
zfs_vdev_scrub_max_active 2
zfs_vdev_scrub_min_active 1
zfs_vdev_sync_read_max_active 10
zfs_vdev_sync_read_min_active 10
zfs_vdev_sync_write_max_active 10
zfs_vdev_sync_write_min_active 10
zfs_vdev_write_gap_limit 4096
zfs_zevent_cols 80
zfs_zevent_console 0
zfs_zevent_len_max 128
zil_replay_disable 0
zil_slog_limit 1048576
zio_delay_max 30000
zio_requeue_io_start_cut_in_line 1
zvol_inhibit_dev 0
zvol_major 230
zvol_max_discard_blocks 16384
zvol_prefetch_bytes 131072
无法弄清楚出了什么问题。
P.S。：arc_reclaim一直是CPU用户中的佼佼者。