Recovering a failed (SSD) hard drive. Unknown partition type.

[jdow]

On 2011/12/27 19:09, fred smith wrote:
> On Tue, Dec 27, 2011 at 08:02:07PM -0700, linux guy wrote:
>> Is there any way to sniff out the old partition table ?    What would
>> I need other than the partition table sizes ?    I know I had boot,
>> swap and / partitions...
>
> FYI:
>
> A year or so ago I had a USB HD with 200-300 gigs of irreplaceable
> data on it, formatted as (iirc) ext3. then I accidentally (some
> might say "stupidly") did a DOS format on the drive. MAJOR OOPS.
>
> I tried some free tools to recover files, and didn't find them very
> helpful (one of 'em saved bazillions of files with no useful filenames).
>
> googling around I found a company doing business in INdia selling
> software that will recover windows/dos/mac/linux filesystems, and can
> run on windows or linux. not finding anything else promising, I sprung
> for the 50 bucks.
>
> the software is somewhat flaky, isn't necessarily trivial to use,
> some of the options don't work in intuitive ways. but to shorten this
> long story, I managed to recover pretty much everything that was on
> the drive, after banging on it for a few days.
>
> I had some questions about how to use the software that I sent
> via email to their support email address, a couple of times, and have
> yet to receive any response from them, so it's clearly a case of
> caveat emptor.
>
> As best as I can remember, it was called "Recover Data for Linux".
>
> So, if you've got a hosed partition table, you may be in a similar
> position to what I was in, so maybe, just maybe, it would be helpful
> for you.
>
> YMMV! I'm not providing any warranties.

There is no trivial way to dig this information out. What you have to do
is read the descriptions of the low level filesystem storage formats and
how mkfs for that filesystem works. With the ext series several copies
exist if the information you need can be found on the disk. You have to
search for it. That can lead to an exhaustive search worst case. Best case
you can calculate about where they should be and limit the search area.
Once you find one you need to determine its basic data, start block and
end block sort of thing. If it's not one partition for the full disk you
must then fuss around and find the next one, lather rinse repeat. Once you
have all that information present you need to hand craft a block zero entry.
The fdisk sort of tools may work and may clobber key information. The Linux
fdisk is nicer in this regard than the winders tool. (I have used the
Microsoft "DiskDoctor" tool for this recovery at least once - got the whole
disk back because I had a REAL good idea of what the partition table should
have looked like. I've never successfully recovered a Linux disk. The one
time I needed to I was too early in my learning curve and too much had been
destroyed by an Adaptec SCSI card bug that killed one byte in maybe a million
on every file write. Um, I've recovered Amiga FFS partitions in the past
with amazing ease. But, then, I took part in some of the design for its
partitioning table.)

You have your work cut out for you, Grasshopper. This is especially true if
you've had multiple different partitionings on that disk.

{^_^}