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Old 24th July 2011
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jggimi jggimi is offline
More noise than signal
 
Join Date: May 2008
Location: USA
Posts: 7,977
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If what you describe is accurate -- and that is only what I can determine from your posting here -- your drive's electronics are not operating properly. If your power failure included either a power surge or a period of low voltage (or missing phases of AC), this might be the cause. But your drive's electronics are at least functioning, as the device does respond to I/O requests, sometimes successfully.

As for your question on "mounts" -- Whatever is occurring has nothing to do with a mount. Mounts are merely logical attachments of filesystems to the OS.

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I do not clearly understand how you ended up with an "i" partition on wd1, but based on your technical background as presented in this thread, I will assume you are using a foreign MBR partition rather than a BSD disklabel on the drive -- the OS will create a virtual disklabel and assign foreign partitions it recognizes to BSD partitions beginning with "i'. And, whether or not this partition was ever actually an FFS filesystem or not is now immaterial - your kernel messages alone are proof of hardware problems -- an inability to read some sectors.

Since your forced, read only mount succeeded, the drive was able to return the sectors containing the primary superblock, which begins at sector #8.

When attempting to read the root directory (inode #2, if this is an FFS filesystem), your "ls" command appeared to hang. Understand that as the drive spins, the electronics may attempt to read the same sector repeatedly, in an attempt to extract valid information. Dozens, or hundreds of times. It must wait for a complete rotation of the drive each time it tries, and that is relatively slow. Eventually, kernel messages will be produced, showing timeouts (from retrying reads over and over, and the OS gives up waiting) and read errors (when the electronics on the drive gives up before the OS does). If you issue the "ls" command from the console, you would see these kernel messages appear while you waited.

Unfortunately, with the root inode unreadable, there is not much further you yourself will be able to do to extract useful data from the drive. If the root directory were available, you might be able to extract undamaged files, and traverse other undamaged directories. But it is not.

A skilled technician may be able to copy undamaged sectors from the drive, and reassemble some of the content into meaningful files. But that would be a manual, difficult, and long effort, with no guarantees.

As for your unreadable sectors, some of them might be readable by commercial laboratories that specialize in data recovery from disk drives. This would be many thousands of Dollars or Euros, and of course there are no guarantees, depending upon the underlying physical damage to the media.

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If you wish to give up on the existing data on the drive, you may start destructive testing, and see if the drive can be returned to useful function. To do that, install e2fsprogs, dismount /backup, and use the badblocks program against the entire drive, rwd1c or wd1c, I can't remember which badblocks prefers. Use -p 1, so that badblocks continues to run until no new failures are discovered -- so that all bad blocks have been successfully replaced with spare sectors, and -w, so that badblocks writes and tests various bit patterns. See badblocks(8) for details.

Last edited by jggimi; 24th July 2011 at 07:50 PM.
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