Like suggested in the comments
#!/bin/sh
for i in `seq 8`;
do ssh w$i 'uptime;
ps -elf|grep httpd|wc -l;
free -m;
mpstat';
done &
pid=$!
sleep 2
kill -9 $pid
In this version, one ssh process may stay alive forever. So maybe it would be better to kill each ssh command separately:
#!/bin/sh
for i in `seq 8`;
do ssh w$i 'uptime;
ps -elf|grep httpd|wc -l;
free -m;
mpstat' &;
pid=$!
sleep 0.3
kill $pid
done