Absolute newbie here.

I have a WD External USB device, so I pull the drive out and it's SATA, I throw it into my CentOS 5 box. In the LVM I can see the new device, /dev/sda & /dev/sdb as well as the VolGroup00 with the primary drive. I would like to add this newly added SATA drive, FAT32, as part of my CentOS 5 file server using SAMBA, but the problem is that I have data on this newly added drive, can I mount it without loosing the data by Initializing the Entity, or do I have to back it up first?

Once I am at the point of mounting, how do I do this as well? I have done this:

# mount -t vfat /dev/sdb /mnt/ExtData

and receive this message:

mount: /dev/sdb already mounted or /mnt/ExtData busy

So I am not sure if I even have the concept down. Help please

Backups are always a good idea, even when things don't seem like they can go wrong.

Are you sure it's /dev/sda and /dev/sdb, what are the servers normal hard drives? Also give the output of the mount command, that will show if /dev/sdb is already mounted or if /mnt/ExtData is already in use. Also mount /dev/sdb isn't valid, with hard drives you should only be able to mount the partitions on it, so it's more likely to be something along the lines of /dev/sdb1 or /dev/sdb2.

yeah I'm sure. I actually pulled the drive out, copied it, put the drive back in and mounted it and junk through the lvm gui.

As I requested before, the output of the mount command could help here. For example here is the mount command performed on one of the VPS on my own server.

[*******@********** ~]$ mount
/dev/xvda2 on / type ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/xvda3 on /tmp type ext3 (rw,noexec,nosuid,nodev)
/dev/xvda1 on /boot type ext3 (rw)
tmpfs on /dev/shm type tmpfs (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)

The xv section of r3sistance's post may confuse many so I will post a more typical example:

But there is still something a little odd. sdX is a physical drive while sdX1 is a partition(X being an integer). You are listing sda and sdb which would indicate two physical drives. In my example there are two physical drives hda(pata) and sda(sata). Each has multiple partitions, which is why you seen hda1,hda5,etc.