raid and cgd

[Alexander Nasonov <alnsn%yandex.ru@localhost>]

My raid is made of two disks dk8 and dk9. When there is an activity on cgd,
dk8 and dk9 shows more than 2x bytes each than cgd. Why is that?

$ systat 2
:vmstat

Disks: seeks xfers bytes %busy                   msix1 vec 4         2048 fmin
   wd0        1525   71M  66.8                   msix2 vec 0         2730 ftarg
   dk3              1203   0.3                   msix2 vec 1              itarg
   wd1        1524   71M  59.3                   msix2 vec 2           75 wired
   dk4                                           msix2 vec 3              pdfre
   dk5                                           msix2 vec 4              pdscn
   dk6
   dk7
   dk9        1524   71M  59.8
  dk10
   dk0
   dk1
   dk2
   dk8        1524   71M  67.3
  dk11
 raid0         761   24M  86.9
  cgd0         761   24M  99.5

-- 
Alex