High fragmentation on zpool log

[Kai Gallasch]

Hi.

Today I had a look at the zpool of a server (FreeBSD 10.2, GENERIC
kernel, 100d uptime, 96GB RAM) I recently installed.

The pool has eight SAS drives in a raid 10 setup (concatenated mirror
pairs) and uses a cache and a mirrored log.

The log and cache both are on a pair of Intel SSDs.

# gpart show -l da9
=>       34  195371501  da9  GPT  (93G)
         34          6       - free -  (3.0K)
         40   16777216    1  log-BTTV5234003K100FGN  (8.0G)
   16777256  178594272    2  cache-BTTV5234003K100FGN  (85G)
  195371528          7       - free -  (3.5K)


Is 85% fragmentation of the log device something to worry about?

Why does zpool list show so unrealistic values for FREE and CAP?
Is this normal?

Atached: Some output of zpool list.

Regards,
Kai.


(zpool list -v output, ommited columns: EXPANDSZ.,DEDUP,
HEALTH, ALTROOT)

NAME                             SIZE  ALLOC   FREE  FRAG  CAP
rpool                           7.25T   440G  6.82T    4%   5%
  mirror                        1.81T   110G  1.71T    4%   5%
   gpt/rpool-WMC160D0SVZE          -      -      -      -    -
   gpt/rpool-WMC160D8MJPD          -      -      -      -    -
  mirror                        1.81T   110G  1.70T    4%   5%
   gpt/rpool-WMC160D9DLL2          -      -      -      -    -
   gpt/rpool-WMC160D23CWA          -      -      -      -    -
  mirror                        1.81T   110G  1.71T    4%   5%
   gpt/rpool-WMC160D94930          -      -      -      -    -
   gpt/rpool-WMC160D9V5LW          -      -      -      -    -
  mirror                        1.81T   110G  1.71T    4%   5%
   gpt/rpool-WMC160D9ZV0S          -      -      -      -    -
   gpt/rpool-WMC160D5HFT6          -      -      -      -    -
  mirror                        7.94G  43.2M  7.90G   85%   0%
   gpt/log-BTTV523401U4100FGN      -      -      -      -    -
   gpt/log-BTTV5234003K100FGN      -      -      -      -    -
cache                              -      -      -      -    -
  gpt/cache-BTTV5234003K100FGN  85.2G   142G  16.0E    0%   166%
  gpt/cache-BTTV523401U4100FGN  85.2G   172G  16.0E    0%   202%



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