iostat and watching disk performance for Promise RAID..

adp dap99 at i-55.com
Tue Mar 9 12:36:15 PST 2004


My disk device is /dev/ar0:

# mount
/dev/ar0s1a on / (ufs, local)
/dev/ar0s1h on /home (ufs, local, soft-updates)
/dev/ar0s1e on /tmp (ufs, local, soft-updates)
...

Yet iostat shows /dev/adX:

n# iostat 5
      tty             ad0              ad4              ad6             cpu
 tin tout  KB/t tps  MB/s   KB/t tps  MB/s   KB/t tps  MB/s  us ni sy in id
   0    3  0.00   0  0.00   0.00   0  0.00   0.00   0  0.00   2  2 26  1 69
   0  448  0.00   0  0.00  15.43  24  0.37  14.80  26  0.37   4  0  9  4 84
   0  541  0.00   0  0.00   6.67   1  0.00   6.00   3  0.02  12  0 16  6 66
   0  730  0.00   0  0.00   4.84   6  0.03   5.67   9  0.05   4  0 12  8 77
   0  483  0.00   0  0.00   2.00   0  0.00   2.00   0  0.00   9  0 10  5 76
 ...

Is iostat simply breaking out my RAID-1 (/dev/ar0) into its two component
drives? If I had three drives composing /dev/ar0 would I then see ad0, ad4,
adX?

/dev/ad6 here is just a drive we use for short-term backups, and is not
RAID.

I just want to confirm. Thanks!




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