harddisk failed strangely, badly need to recover data

[Zhang Weiwu]

Dear list. I added a 160 GB harddisk to the FreeBSD server several days
ago. I have setup only one slice on it (/dev/ad6s1) and it has two
partitions on it.

/dev/ad6s1c is used as swap
/dev/ad6s1d is used as /var

Today I decided to reboot the FreeBSD server because I messed up nfs
settings. After restart /var/ failed to mount. I was brought to a shell
where I am suggested to do fsck manually. fsck manually couldn't help
either:

        [root at exupery /home/zhangweiwu]# fsck /dev/ad6s1d
        ** /dev/ad6s1d
        Cannot find file system superblock
        
        LOOK FOR ALTERNATE SUPERBLOCKS? [yn] y
        
        32 is not a file system superblock
        28780512 is not a file system superblock
        57560992 is not a file system superblock
        86341472 is not a file system superblock
        115121952 is not a file system superblock
        143902432 is not a file system superblock
        172682912 is not a file system superblock
        201463392 is not a file system superblock
        230243872 is not a file system superblock
        259024352 is not a file system superblock
        287804832 is not a file system superblock
        SEARCH FOR ALTERNATE SUPER-BLOCK FAILED. YOU MUST USE THE
        -b OPTION TO FSCK TO SPECIFY THE LOCATION OF AN ALTERNATE
        SUPER-BLOCK TO SUPPLY NEEDED INFORMATION; SEE fsck(8).

I tried to fix it by do inga harddisk bad-sector checking for the
beginning 1GB of the harddisk (result is successful, no bad sector in
the beginning 1GB). The data on the harddisk is not modified/erased
during checking

Use 'dd if=/dev/ad6 bs=32k | hd -v | grep "19 01 54 19"' to locate the
super block and do some calculation to get the superblock sector number
(following an Internet article) and pass it to fsck_ufs like this:
'fsck_ufs -b 12032 /dev/ad6s1d'. Under a lot of time pressure I
confirmed twice with 'y' for the following questions of whether or not
to set some values to default without fully understanding the questions,
later seeing more questions I stopped fsck by Ctrl+C.

Before running fsck I tried to backup the first 100MB data of /dev/ad6
using dd which should help me recover even if I destroyed superblock
of /dev/ad6s1d. Later I realized I have by mistake only backed up the
beginning 4.0MB of /dev/ad6

Is it possible now for me to recover the data in /var/
(especially /var/backups)? Thanks a lot in advance!

P.S. I am being really unlucky because this harddisk is mostly used for
backup purpose and thus is not backed up (who back up the back-up
harddisk?) and when I today failed to mount this harddisk, 0.5 hour
later the server being backed up by it has got an accident and need the
backup data to recover.