lvm/mdadm oddness

gistfile1.txt

# cat /proc/mdstat 
Personalities : [linear] [multipath] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] 
md4 : active raid1 sda2[0] sdb2[1]
      1220939904 blocks [2/2] [UU]
      
md3 : active raid10 sda1[0] sdb1[2] sdd[1] sdc[3]
      1465146880 blocks 64K chunks 2 near-copies [4/4] [UUUU]
      
unused devices: <none>
# pvs
  PV         VG    Fmt  Attr PSize PFree  
  /dev/md4   raid1 lvm2 a-   1.14t 654.38g
# lvs
  LV              VG    Attr   LSize   Origin Snap%  Move Log Copy%  Convert
  backup          raid1 -wi-ao 400.00g                                      
  lucid-root      raid1 -wi-ao  10.00g                                      
  virtualmachines raid1 -wi-a- 100.00g
# grep virtualmachines /etc/fstab
/dev/mapper/raid10-virtualmachines      /virtual-machines       ext4    relatime,errors=remount-ro 0       1
#/dev/raid1/virtualmachines     /virtual-machines       ext4    relatime,errors=remount-ro 0       1
# mount /virtual-machines/
# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/raid1-lucid--root
                      9.9G  3.0G  6.4G  32% /
none                  4.0G  280K  4.0G   1% /dev
none                  4.0G     0  4.0G   0% /dev/shm
none                  4.0G   80K  4.0G   1% /var/run
none                  4.0G     0  4.0G   0% /var/lock
none                  4.0G     0  4.0G   0% /lib/init/rw
/dev/mapper/raid1-backup
                      394G  269G  106G  72% /backup
/dev/mapper/raid10-aptmirror
                      119G   34G   79G  31% /var/spool/apt-mirror
/dev/mapper/raid10-virtualmachines
                       99G   49G   45G  53% /virtual-machines
# find /virtual-machines/ -maxdepth 1 -type d
/virtual-machines/
/virtual-machines/bucket-of-errors
/virtual-machines/lost+found
# umount /virtual-machines/
# mount /dev/raid1/virtualmachines /virtual-machines
# find /virtual-machines/ -maxdepth 1 -type d
/virtual-machines/
/virtual-machines/lost+found
# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/raid1-lucid--root
                      9.9G  3.0G  6.4G  32% /
none                  4.0G  280K  4.0G   1% /dev
none                  4.0G     0  4.0G   0% /dev/shm
none                  4.0G   80K  4.0G   1% /var/run
none                  4.0G     0  4.0G   0% /var/lock
none                  4.0G     0  4.0G   0% /lib/init/rw
/dev/mapper/raid1-backup
                      394G  269G  106G  72% /backup
/dev/mapper/raid10-aptmirror
                      119G   34G   79G  31% /var/spool/apt-mirror
/dev/mapper/raid1-virtualmachines
                       99G  188M   94G   1% /virtual-machines
#