[mythtv-users] recovery of files and filenames from ext4 partition

[Mike Perkins]

On 17/02/15 13:45, John Pilkington wrote:
> On 17/02/15 10:35, Hika van den Hoven wrote:
>> Hoi Mark,
>>
>> Tuesday, February 17, 2015, 10:38:14 AM, you wrote:
>>
>>> Just thought I would give a quick update on where I got to with my crashed
>>> hard disk.
>>
>>> Testdisk worked quite well for me (thanks Doug). I had about 1.8TB of
>>> recordings on the drive. On the first pass Testdisk was able to recover 387
>>> of 498 missing recordings including one of two recordings that I really
>>> wanted (most things I really want get watched quickly after recording, the
>>> stuff that sits there for a long time tends to be well down the viewing
>>> order). The recordings were missing their file names and extensions but I
>>> wrote a script that checked the file size and the number of frames and
>>> matched those to the database to get the correct names back (I assumed
>>> everything was mpg because I only had recordings on the drive and I deleted
>>> everything less than a couple hundred MB because the preview png get
>>> regenerated automatically anyway).
>>
>>> After doing a few more passes with Testdisk I got another 62 recordings back
>>> that also appear to be 100% intact (and the second of the two recordings I
>>> really wanted). I also got another 22 recordings where the filesize was
>>> correct but the frame count was off by a small amount so I am assuming there
>>> may be a small amount of corruption in those files, although I have not been
>>> able to pick it yet on the quick once-over I did.
>>
>>> That left about 27 recordings completely toast. Testdisk is still actually
>>> working on the disk trying to read the faulty area's but it is really really
>>> slow at this stage, only getting about a single byte back about every 10hrs
>>> so it's pretty much done (there is about 75MB it is unable to read at last
>>> count which is down from about 100Mb at the start). I might let it run a
>>> little longer but figure at this stage there is nothing to be gained, the
>>> lost recordings are nothing that particularly concern me.
>>
>>> The only other loss was a missed recording when the backend crashed and
>>> wouldn't reboot, other than that I would have gotten away unscathed.
>>
>>> TL:DR - Testdisk did a great job recovering lost files from crashed hard
>>> disk.
>>
>> Could you maybe create a wiki entry for future reference. With your
>> scripts etc.?
>>
>
> Hmm:  yesterday I cleared a small directory with rm *.  Today, having cd-ed to a
> recordings directory, I pressed 'Return'.  Guess what...
>
> It's an xfs partition, default for el7 clones, and TestDisk doesn't say it does
> that.  I thought hxtools might be worth a try, but the rpm is a cut-down version
> that doesn't include xfs_irepair. Looks as if it would be an 'interesting'
> learning experience, anyway.  I suspect I'm going to be saying 'it's only tv'
> too.  Lots and lots of DVDs to watch, and books to read...   and recent large
> commits to master to try.
>
> I see there's a new build for ubuntu trusty.  I was waiting to try that, on the
> test box, before 'production'.  But now there's lots of disk space...  :-)
>
One rule I never forget: When recovering a disk, NEVER delete ANYTHING until you 
have completely salvaged everything off the bad disk and are sure you don't want 
anything else... then do a backup of what you saved!

-- 

Mike Perkins