On a ubuntu server I own, I am running out of space. When I ran

sudo parted /dev/sda -l

to find all available drives, I got this:

Model: ATA ST31000528AS (scsi)
Disk /dev/sda: 1000GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type      File system  Flags
 1      1049kB  256MB   255MB   primary   ext2         boot
 2      257MB   1000GB  1000GB  extended
 5      257MB   1000GB  1000GB  logical                lvm


Model: Linux device-mapper (linear) (dm)
Disk /dev/mapper/server--vg-swap_1: 2135MB
Sector size (logical/physical): 512B/512B
Partition Table: loop

Number  Start  End     Size    File system     Flags
 1      0.00B  2135MB  2135MB  linux-swap(v1)


Model: Linux device-mapper (linear) (dm)
Disk /dev/mapper/server--vg-root: 998GB
Sector size (logical/physical): 512B/512B
Partition Table: loop

Number  Start  End    Size   File system  Flags
 1      0.00B  998GB  998GB  ext4

I understand /dev/mapper/server--vg-root is the filesystem, and /dev/sda1 has some stuff related to GRUB.

But, what about /dev/sda2 and /dev/sda5? When I tried to mount /dev/sda2, it said that I needed to specify the file system, which according to the table, is nonexistent. So, is it safe to format this with, say ext4 and mount it?

Also, when I tried to mount /dev/sd5, it gave me this error:

mount: unknown filesystem type 'LVM2_member'

I assume it is NOT save to reformat this. If I'm wrong, then that would be great, because I could save some space. Please let me know either way. Thanks in advance!

UPDATE: Here is the result of mount:

/dev/mapper/server--vg-root on / type ext4 (rw,errors=remount-ro)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
none on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
udev on /dev type devtmpfs (rw,mode=0755)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755)
none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880)
none on /run/shm type tmpfs (rw,nosuid,nodev)
/dev/sda1 on /boot type ext2 (rw,acl)
/dev/sda1 on /media/hd2 type ext2 (rw)