zdb -S でわかるらしいのでやってみた。
% zpool status -v pool: tank state: ONLINE status: The pool is formatted using an older on-disk format. The pool can still be used, but some features are unavailable. action: Upgrade the pool using 'zpool upgrade'. Once this is done, the pool will no longer be accessible on older software versions. scan: scrub repaired 0 in 6h35m with 0 errors on Thu May 5 10:04:39 2011 config: NAME STATE READ WRITE CKSUM tank ONLINE 0 0 0 raidz1-0 ONLINE 0 0 0 ada1s2 ONLINE 0 0 0 ada2s2 ONLINE 0 0 0 ada3s2 ONLINE 0 0 0 logs label/zil ONLINE 0 0 0 errors: No known data errors % zpool iostat capacity operations bandwidth pool alloc free read write read write ---------- ----- ----- ----- ----- ----- ----- tank 1.06T 898G 15 24 120K 299K % zpool iostat -v capacity operations bandwidth pool alloc free read write read write ----------- ----- ----- ----- ----- ----- ----- tank 1.06T 898G 15 24 120K 299K raidz1 1.06T 898G 15 24 120K 251K ada1s2 - - 4 11 163K 127K ada2s2 - - 4 11 161K 127K ada3s2 - - 4 11 161K 127K label/zil 204K 1.95G 0 0 14 48.5K ----------- ----- ----- ----- ----- ----- ----- % zdb -S tank Simulated DDT histogram: bucket allocated referenced ______ ______________________________ ______________________________ refcnt blocks LSIZE PSIZE DSIZE blocks LSIZE PSIZE DSIZE ------ ------ ----- ----- ----- ------ ----- ----- ----- 1 336K 9.61G 9.61G 9.67G 336K 9.61G 9.61G 9.67G 2 6.02K 215M 215M 216M 12.7K 442M 442M 444M 4 592 9.52M 9.52M 9.64M 2.78K 43.3M 43.3M 43.9M 8 223 1.77M 1.77M 1.83M 2.13K 18.2M 18.2M 18.7M 16 19 39K 39K 42.6K 408 854K 854K 931K 32 7 35K 35K 36.6K 315 1.96M 1.96M 2.03M 64 5 130K 130K 131K 503 14.9M 14.9M 15.0M 128 1 512 512 682 178 89K 89K 119K 256 3 1.50K 1.50K 2.00K 1.17K 598K 598K 797K 512 3 1.50K 1.50K 2.00K 2.16K 1.08M 1.08M 1.44M 1K 1 512 512 682 1.20K 612K 612K 816K Total 343K 9.83G 9.83G 9.89G 359K 10.1G 10.1G 10.2G dedup = 1.03, compress = 1.00, copies = 1.01, dedup * compress / copies = 1.02 %
表の意味はよくわからんが、最後の1行だけみると全く効果なしのようだ。