Can't read past apparent/erroneous EOF marker but can append

[Jeff Archambeault]

Hi,

Is this the right mailing list to post this message to?

I have 2 large files that behave strangely and are in an inconsistent state.
Both 'stat' and reading the directory show these files at one length, and yet
only a small fraction of that length is accessible.
When you read as much of the file as you can from the beginning, using
high-level I/O routines, the stopping point looks like the end of the file.
When you do the same with low-level I/O routines, you get error #5 (I/O error)
at the same location, which seems to be at a block boundary.
I believe that you can append to the end of the file, but you can't read
past this early stopping point.

filename   |   file length     |  stopping point
--------------+---------------------+---------------------
inbox       | 19564798758  | 322543616
sent-mail | 1577130211    |  276058112

The question is: how do I get the full contents of both files back?
If I can't, how can I salvage the most from these files?

Environment Background:

Samsung 530U notebook
Intel Core i5-2467M 1.6GHz CPU quad core
500GB HDD (+16GB SSD, unused), 4GB RAM
Linux Mint Cinnamon 17
3.13.0-24-generic x86_64 kernel
ext4 filesystem
Linux version 3.13.0-24-generic (buildd at panlong) (gcc version 4.8.2 (Ubuntu
4.8.2-19ubuntu1) ) #46-Ubuntu SMP Thu Apr 10 19:11:08 UTC 2014
(Ubuntu 3.13.0-24.46-generic 3.13.9)

File 1: mutt inbox
ls reports file size of 19564798758
~/Mail\: stat inbox
  File: ‘inbox’
  Size: 19564798758     Blocks: 38212824   IO Block: 4096   regular file
Device: 802h/2050d      Inode: 1966123     Links: 1
Access: (0755/-rwxr-xr-x)  Uid: ( 1000/    walt)   Gid: ( 1000/    walt)
Access: 2014-10-29 17:56:17.167131303 -0400
Modify: 2014-08-28 10:46:39.365538078 -0400
Change: 2014-08-28 10:46:39.365538078 -0400
 Birth: -

walt-laptop Mail # cp inbox /mnt/sda6
cp: error reading ‘inbox’: Input/output error
cp: failed to extend ‘/mnt/sda6/inbox’: Input/output error
destination size 322543616

File 2: sent-mail
ls reports file size of 1577130211
~/Mail\: stat sent-mail
  File: ‘sent-mail’
  Size: 1577130211      Blocks: 3080344    IO Block: 4096   regular file
Device: 802h/2050d      Inode: 1966186     Links: 1
Access: (0755/-rwxr-xr-x)  Uid: ( 1000/    walt)   Gid: ( 1000/    walt)
Access: 2014-11-04 11:40:07.268161539 -0500
Modify: 2013-07-12 12:05:01.000000000 -0400
Change: 2014-07-30 15:19:59.302391052 -0400
 Birth: -

(same errors from copy command as with 'inbox')
destination size when copied: 276058112

Thanks in advance for any information.

Sincerely,
Jeff Archambeault
http://www.barkeaterstudios.org/
jeff at barkeaterstudios.org