Re: How to recover a damaged partition
On Wednesday 21 January 2015 21:53:23 Kevin O'Gorman did opine
And Gene did reply:
> I'm working with new 4TB drives, and one of them just had a bad spot in
> a fairly awkward place.
> The very first block of an ext4 partition was unreadable, and caused
> problems in booting, as well as anything else that wanted to scan
> partitions.
Warranty it now. Thats a surface defect that, since its scanned back and
forth across almost anytime the disk is read or written to, causing head
damage that will in time ruin the rest of the platter surfaces.
The bad area will grow with time, and has in every instance I have
encountered it. I am a packrat and from my first hard drive, I have a
printout of the badsectors file descriptor from an ST238R drive. But I
had to keep adding to it, and when I was out of segment room in that
filesystem (os9 level 1) I bit the bullet and replaced both the drive and
controller with scsi stuff. I never realized what a headache I'd had with
lost data until I didn't have it anymore.
> I overwrote the first 4K with zeroes, deleted the partition (with
> gdisk) and created a new unformatted partition to cover the area. Now
> that partition passes a read test, and I'm checking the other
> partitions.
>
> The damaged partition has been inactive for a while, so I'm quite sure
> I have adequate backups. But now seems to be a time for me to learn
> -- lots of things have been going wrong, and I've been learning how to
> cope.
>
> So I wonder if there's a way to get that partition back, at least in
> part, without using my backups.
>
> Any hints, pointers, tutorials, or opinions welcome.
Warranty it, and then use your backups to restore its replacement. You
will be way ahead of the game in terms of the time spent messing with it,
and the headaches recovering from its mistakes.
The fact that the drive has not substituted a spare block or 20 says it
has probably done so already and has no more spares. A query with
smartctl would I suspect, confirm it. Most drives maintain a spare sector
area that is lots more than the 4k you are missing. For a 4Tb drive,
probably a gigabyte in those spare reserves.
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS
Reply to: