Harddisk Problem

[PsYxAkIaS (FreeBSD)]

Hello,

We just installed and mounted a 2nd HDD(secondary ide channel) on a Dedicated Server on FreeBSD 4.8 and look what it gives:

] df 
Filesystem 1K-blocks   Used  Avail Capacity Mounted on
/dev/ad0s1a  2015918  52114 1802532   3%  /
/dev/ad0s1f 22479870 16924774 3756708  82%  /usr
/dev/ad0s1e  4031950  73418 3635976   2%  /var
procfs       4    4    0  100%  /proc
/dev/ad2s1e 76958474    4 70801794   0%  /drive2

] df -h
Filesystem  Size  Used Avail Capacity Mounted on
/dev/ad0s1a  1.9G  51M  1.7G   3%  /
/dev/ad0s1f  21G  16G  3.6G  82%  /usr
/dev/ad0s1e  3.8G  72M  3.5G   2%  /var
procfs    4.0K  4.0K   0B  100%  /proc
/dev/ad2s1e  73G  4.0K  68G   0%  /drive2

] cat /etc/fstab
# See the fstab(5) manual page for important information on automatic mounts
# of network filesystems before modifying this file.
#
# Device                Mountpoint      FStype  Options         Dump    Pass#
/dev/ad0s1b             none            swap    sw              0       0
/dev/ad0s1a             /               ufs     rw              1       1
/dev/ad0s1f             /usr            ufs     rw              2       2
/dev/ad0s1e             /var            ufs     rw              2       2
/dev/acd0c              /cdrom          cd9660  ro,noauto       0       0
proc                    /proc           procfs  rw              0       0
/dev/ad2s1e             /drive2         ufs     rw              2       2

The problem is that from 73GB (80gb hdd) it only sees free 68GB.

How can i check if it has bad sectors? A friend suggested me low-level format but I never done that before under unix.

Also, do i need to be in single-user (I dont have physical access, only remote root via ssh).


Thank you.