Parsing iostat output

Question 1

If VG00 is always present in split lines, you could do it like this:

sed '/VG00/ { N; s/\n// }'

With the copy/pasted text I have the following aligns the columns (GNU sed and BSD sed):

sed '/VG00/ { N; s/\n//; s/ \{5,\}/     /; }'

Output:

Device:         rrqm/s   wrqm/s   r/s   w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await  svctm  %util
sda               0.00     2.40  0.01  3.92     0.16    25.28    12.95     0.05   12.81   6.58   2.58
sda1              0.00     0.00  0.00  0.00     0.00     0.00    25.86     0.00    6.57   5.38   0.00
sda2              0.00     2.40  0.01  3.92     0.16    25.28    12.95     0.05   12.81   6.58   2.58
sdb               0.00     0.00  0.00  0.00     0.00     0.00     8.00     0.00   30.37  20.16   0.00
VG00-LogVol00     0.00     0.00  0.00  0.70     0.02     2.79     8.04     0.02   23.72   3.71   0.26
VG00-LogVol04     0.00     0.00  0.00  4.31     0.03    17.26     8.01     0.07   16.74   4.32   1.87
VG00-LogVol03     0.00     0.00  0.00  0.24     0.00     0.98     8.01     0.01   21.37   8.52   0.21
VG00-LogVol08     0.00     0.00  0.00  0.00     0.00     0.00     8.00     0.00   14.03   2.31   0.00
VG00-LogVol01     0.00     0.00  0.00  0.00     0.00     0.00     8.03     0.00  127.25   1.17   0.00
VG00-LogVol07     0.00     0.00  0.00  0.00     0.00     0.00     8.00     0.00    2.42   1.72   0.00
VG00-LogVol06     0.00     0.00  0.00  0.80     0.01     3.21     8.02     0.01   10.28   4.89   0.39
VG00-LogVol02     0.00     0.00  0.01  0.26     0.10     1.04     8.52     0.01   52.88   6.01   0.16
VG00-LogVol05     0.00     0.00  0.00  0.00     0.00     0.00     8.00     0.00    3.73   0.33   0.00

Question 2

I'd go for

sed -e '/^\([^[:space:]]\+\)$/{N;s/\n//;}'

assuming the device lines have no whitespace.

But I'd also look into the possibility to influence iostat and make it produce different output. I don't know the options there, though.