Exploring the ZFS arc..?

ARC – adaptive replacement cache …

well there is no dedicated readzilla (L2-ARC) or logzilla (ZIL) for my test SAN (NexentaStor)

i was curios to see the dataset of ARC content and ended up with this script,

admin@nssan:~$ ./arc_summary.pl
System Memory:
         Physical RAM:  8173 MB
         Free Memory :  770 MB
         LotsFree:      127 MB

ZFS Tunables (/etc/system):

ARC Size:
         Current Size:             5613 MB (arcsize)
         Target Size (Adaptive):   5613 MB (c)
         Min Size (Hard Limit):    893 MB (zfs_arc_min)
         Max Size (Hard Limit):    7149 MB (zfs_arc_max)

ARC Size Breakdown:
         Most Recently Used Cache Size:          44%    2497 MB (p)
         Most Frequently Used Cache Size:        55%    3116 MB (c-p)

ARC Efficency:
         Cache Access Total:             5292249
         Cache Hit Ratio:      96%       5110509        [Defined State for buffer]
         Cache Miss Ratio:      3%       181740         [Undefined State for Buffer]
         REAL Hit Ratio:       93%       4939551        [MRU/MFU Hits Only]

         Data Demand   Efficiency:    97%
         Data Prefetch Efficiency:    62%

        CACHE HITS BY CACHE LIST:
          Anon:                        1%        97516                  [ New Customer, First Cache Hit ]
          Most Recently Used:         14%        716979 (mru)           [ Return Customer ]
          Most Frequently Used:       82%        4222572 (mfu)          [ Frequent Customer ]
          Most Recently Used Ghost:    0%        11400 (mru_ghost)      [ Return Customer Evicted, Now Back ]
          Most Frequently Used Ghost:  1%        62042 (mfu_ghost)      [ Frequent Customer Evicted, Now Back ]
        CACHE HITS BY DATA TYPE:
          Demand Data:                52%        2706672
          Prefetch Data:               1%        95218
          Demand Metadata:            43%        2198797
          Prefetch Metadata:           2%        109822
        CACHE MISSES BY DATA TYPE:
          Demand Data:                31%        57731
          Prefetch Data:              31%        57053
          Demand Metadata:            33%        60038
          Prefetch Metadata:           3%        6918
———————————————

Advertisements