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 -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: https://lists.debian.org/201501220652.08155.ghesk...@wdtv.com
Re: How to recover a damaged partition
On 21/01/15 09:53 PM, Kevin O'Gorman wrote: 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. 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. -- Kevin O'Gorman #define QUESTION ((bb) || (!bb)) /* Shakespeare */ Please consider the environment before printing this email. If you haven't reformatted the partition, use testdisk on it. Or you can tell fsck to use a backup superblock instead of the one you overwrote with zeros. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: https://lists.debian.org/54c08317.4080...@torfree.net
Re: How to recover a damaged partition
Quoting Kevin O'Gorman (kogor...@gmail.com): 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. 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. Having had a similar problem where the first few blocks of a partition wouldn't read, I used dd to ascertain what I could and couldn't read, and then: Create a blank start of a file: dd bs=512 if=/dev/zero of=/ylarge/image-of-hdd4-skipping-16 count=16 Add the undamaged part of the partition: dd bs=512 if=/dev/hdd4 of=/ylarge/image-of-hdd4-skipping-16 skip=16 seek=16 See if it can be mended: e2fsck -n -f /ylarge/image-of-hdd4-skipping-16 If so, mend it: e2fsck -f /ylarge/image-of-hdd4-skipping-16 Mount it: mount -t ext3 -o ro,loop=/dev/loop0 /ylarge/image-of-hdd4-skipping-16 /mnt Copy off all the files. hdd4 was the failed partition. /ylarge was a filesystem big enough to hold an image of hdd4. Note however that hdd4 was ext3, not ext4. I don't know whether that affects things. Good luck. Cheers, David. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: https://lists.debian.org/20150122045521.ga17...@alum.home
Re: How to recover a damaged partition
On 01/21/2015 06:53 PM, Kevin O'Gorman wrote: 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. 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. -- Kevin O'Gorman #define QUESTION ((bb) || (!bb)) /* Shakespeare */ Please consider the environment before printing this email. Have you tried doing a badblocks on the partition. This will try reading and writing data to the partition to check the disk drive. I generally do this on my drive before deploying. It tends to remove the bad blocks. You can also try grc's Spinrite (cost money) at grc.com -- Joseph Loo j...@acm.org -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: https://lists.debian.org/54c06e22.4080...@aqcm.org
How to recover a damaged partition
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. 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. -- Kevin O'Gorman #define QUESTION ((bb) || (!bb)) /* Shakespeare */ Please consider the environment before printing this email.
