Насколько быстр программный RAID

Быстр и достаточно эффективен.
~# bon_csv2txt < raid-test.csv
Version  1.03      ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
single-drive     4G 36777  79 35290 7.5 25405   7 27698  60 54407 6.5   202   0
raid0-stripe     4G 45815  99 60960 13.5 28002 7.5 39714  88 93861  13 332.3   0
raid1-mirror     4G 273255  60 26907 5.5 18850   5 27927  61 50624 6.5 350.4   0
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files:max:min        /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
single-dr 100:100:0  2591  31 127329  95  1726  15  2640  33 111161  84   332   3
raid0-str 100:100:0  3732  50 132760 99.5  4196 24.5  3741  50 130757 100   844   8
raid1-mir 100:100:0  1667  21 118240  92  1121 12.5  1678  22 121867 96.5   304 3.5

А какой уровень посоветуете для домашней тачки?

дисков 2? IDE? raid-1