S_TIME_FORMAT=ISO iostat -xydt sda sdc 1 | awk -f iostat2csv.awk

iostat2csv.awk

# we should print the header once
BEGIN {
        header = 1
}

# match each block, e.g.
# 2022-06-11T18:42:05+0800
# Device            r/s     rkB/s   rrqm/s  %rrqm r_await rareq-sz     w/s     wkB/s   wrqm/s  %wrqm w_await wareq-sz     d/s     dkB/s   drqm/s  %drqm d_await dareq-sz     f/s f_await  aqu-sz  %util
# sda              0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.00
# sdc              0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.00
#
/^[0-9]+/, /^$/ {
        if ($1 ~ /^[0-9]+/) {
                timestamp = $0
        } else if ($1 ~ /Device/) {
                if (header) {
                        print "Timestamp\t" $0
                        header = 0
                }
        } else if ($1 !~ /^$/) {
                print timestamp "\t" $0
        } else {
        }
}