On Tue, 14 Jan 2020 at 21:25, Theodore Y. Ts'o <tytso@xxxxxxx> wrote: > > On Tue, Jan 14, 2020 at 04:03:53PM +0000, James Courtier-Dutton wrote: > > > > Say I started with 1 disk using LVM with an ext4 partition. > > I then added another disk. Added it to the LVM group, expanded the > > ext4 partition to then fill 2 disks. > > I then added another disk. Added it to the LVM group, expanded the > > ext4 partition to then fill 3 disks. > > Where you using RAID 0, or some more advanced RAID level? > > > One of the disk has now failed. > > How has it failed? It is dead dead dead? Or are there a large number > of sector errors? > > > Are there any tools available for ext4 that could help recover this? > > Note, I am a single user, not a company, so there is no money to give > > to a data recovery company, so I wish to try myself. > > How valuable is your data? The first thing I would recommend, if your > data is worth it (and only you can make that decision) is to create a > new RAID set (using larger disks if that helps reduce the price) so > you can make an block-level image backup using the dd_rescue program. > > If you can, then run e2fsck on the backup copy, and then see what you > can recover from that image set. This will save time (how much is > your time worth?) and perhaps increase the amount of data you can > recover (how much is your data worth?). > > - Ted Hi, Thank you all for the help. I have made some progress. Disk 1 is 100% OK. Disk 2 did dd_rescue and recovered about 30% of the sectors. Disk 3 is 100% OK. I have made images of all of that. LVM worked out what order they went in, and ext4 even let me mount the LVM volume. I have managed to recover a lot of the data, so thank you for the hints. What I would like to do now is find out which files were on Disk 2. I have found the fiemap IOCTL that gives me the logical sectors for the file itself. How do I convert the value from the IOCTL into a physical sector, or at least an offset into the LVM volume? I can then work at that sector 0 to A is on Disk 1, A to B is on Disk 2, and B to C is on Disk 3. For example, this is how it is done on btrfs. What is the equivalent on ext4? $ sudo filefrag -v UEFI_Spec_2_8_final.pdf Filesystem type is: 9123683e File size of UEFI_Spec_2_8_final.pdf is 18586279 (4538 blocks of 4096 bytes) ext: logical_offset: physical_offset: length: expected: flags: 0: 0.. 4537: 9798022.. 9802559: 4538: last,eof UEFI_Spec_2_8_final.pdf: 1 extent found $ sudo btrfs-map-logical -l $[9798022*4096] /dev/nvme0n1p7 mirror 1 logical 40132698112 physical 31475654656 device /dev/nvme0n1p7 $ sudo dd if=/dev/nvme0n1p7 bs=1 skip=31475654656 count=64 2>/dev/null | hexdump -C 00000000 25 50 44 46 2d 31 2e 36 0d 25 e2 e3 cf d3 0d 0a |%PDF-1.6.%......| 00000010 33 30 35 35 31 39 20 30 20 6f 62 6a 0d 3c 3c 2f |305519 0 obj.<</| 00000020 46 69 6c 74 65 72 2f 46 6c 61 74 65 44 65 63 6f |Filter/FlateDeco| 00000030 64 65 2f 46 69 72 73 74 20 31 31 37 39 2f 4c 65 |de/First 1179/Le| 00000040 Kind Regards James
