I created a logical volume (scandata) containing a single ext3 partition. It is the only logical volume in its volume group (case4t). Said volume group is comprised by 3 physical volumes, which are three primary partitions on a single block device (/dev/sdb).

When I created it, I could mount the partition via the block device /dev/mapper/case4t-scandatap1.

Since last reboot the aforementioned block device file has disappeared.

It may be of note -- I'm not sure -- that my superior (a college professor) had prompted this reboot by running sudo chmod -R [his name] /usr/bin, which obliterated all suid in its path, preventing the both of us from sudo-ing. That issue has been (temporarily) rectified via this operation.

Now I'll cut the chatter and get started with the terminal dumps:

$ sudo pvs; sudo vgs; sudo lvs

    Logging initialised at Sat Jan  8 11:42:34 2011  
    Set umask to 0077   
    Scanning for physical volume names  
PV         VG     Fmt  Attr PSize   PFree  
/dev/sdb1  case4t lvm2 a-   819.32G    0   
/dev/sdb2  case4t lvm2 a-   866.40G    0   
/dev/sdb3  case4t lvm2 a-    47.09G    0   
    Wiping internal VG cache  
    Logging initialised at Sat Jan  8 11:42:34 2011  
    Set umask to 0077  
    Finding all volume groups  
    Finding volume group "case4t"  
VG     #PV #LV #SN Attr   VSize VFree  
case4t   3   1   0 wz--n- 1.69T    0   
    Wiping internal VG cache  
    Logging initialised at Sat Jan  8 11:42:34 2011  
    Set umask to 0077  
    Finding all logical volumes  
LV       VG     Attr   LSize Origin Snap%  Move Log Copy%  Convert  
scandata case4t -wi-a- 1.69T                                        
    Wiping internal VG cache  

$ sudo vgchange -a y

Logging initialised at Sat Jan  8 11:43:14 2011
Set umask to 0077
Finding all volume groups
Finding volume group "case4t"
1 logical volume(s) in volume group "case4t" already active
1 existing logical volume(s) in volume group "case4t" monitored
Found volume group "case4t"
Activated logical volumes in volume group "case4t"
1 logical volume(s) in volume group "case4t" now active
Wiping internal VG cache

$ ls /dev | grep case4t

case4t

$ ls /dev/mapper

case4t-scandata  control

$ sudo fdisk -l /dev/case4t/scandata

Disk /dev/case4t/scandata: 1860.5 GB, 1860584865792 bytes
255 heads, 63 sectors/track, 226203 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00049bf5

               Device Boot      Start         End      Blocks   Id  System
/dev/case4t/scandata1               1      226203  1816975566   83  Linux

$ sudo parted /dev/case4t/scandata print

Model: Linux device-mapper (linear) (dm)
Disk /dev/mapper/case4t-scandata: 1861GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type     File system  Flags
 1      32.3kB  1861GB  1861GB  primary  ext3    

$ sudo fdisk -l /dev/sdb

Disk /dev/sdb: 1860.5 GB, 1860593254400 bytes
255 heads, 63 sectors/track, 226204 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000081

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1      106955   859116006   83  Linux
/dev/sdb2          113103      226204   908491815   83  Linux
/dev/sdb3          106956      113102    49375777+  83  Linux

Partition table entries are not in disk order

$ sudo parted /dev/sdb print

Model: DELL PERC 6/i (scsi)
Disk /dev/sdb: 1861GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type     File system  Flags
 1      32.3kB  880GB   880GB   primary  reiserfs          
 3      880GB   930GB   50.6GB  primary                    
 2      930GB   1861GB  930GB   primary

I find it a bit strange that partition one above is said to be reiserfs, or if it matters -- it was previously reiserfs, but LVM recognizes it as a PV.

To reiterate, neither /dev/mapper/case4t-scandatap1 (which I had used previously) nor /dev/case4t/scandata1 (as printed by fdisk) exists. And /dev/case4t/scandata (no partition number) cannot be mounted:

$sudo mount -t ext3 /dev/case4t/scandata /mnt/new

mount: wrong fs type, bad option, bad superblock on /dev/mapper/case4t-scandata,
       missing codepage or helper program, or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

All I get on syslog is: [170059.538137] VFS: Can't find ext3 filesystem on dev dm-0.

Thanks in advance for any help you can offer,
Brian

P.S. I am on Ubuntu GNU/Linux 2.6.28-11-server (Jaunty) (out of date, I know -- that's on the laundry list).