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