Re: 4000GB partition becoming 1801GB after reboot?

[Isolationism]

> If the partition was to start at the next head after the MBR
> (i.e. CHS=0/1/1) and span the whole remaining disk, then the size field
> in the partition table should be 7812425502 or 0x1D1A8271E hex (which
> is too big to fit in 32 bit and would be truncated to 0xD1A8271E).

You've certainly accomplished more calculation than I'm capable of executing!
A very logical approach. Mine was much more "seat-of-my-pants".

In my prior reply, I detailed what I did the first time to recover the disk
successfully. I omitted the fact that I recreated an MSDOS partition first
and attempted to recover to that:

`parted /dev/sdb mklabel msdos`
`parted /dev/sdb rescue 0 -1`

This in fact did still find the partition -- but again, only ~1.8TiB of it
showed up in parted.

Unless the rescue option has different restrictions compared to creation of a
new partition, it was almost certainly case #1 that I described earlier,
where both msdos and gpt partitions simultaneously existed on the same device
-- or a different case, where somehow the gpt partition was somehow
overwritten with an msdos partition -- otherwise I expect I would have been
able to recover the full 4GB using an msdos label, which was not the case.

It is also worth mentioning that there has been no corruption at all of the
280GiB worth of contents on the drive; we have gone over everything with a
fine toothed comb and there is no damage or corruption whatsoever (phew!).

Here is the new partition geometry as you requested:

-------
sectors
-------
Disk /dev/sdb: 7812415488s
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start  End          Size         File system  Name  Flags
 1      63s    7812409494s  7812409432s  xfs

---------
cylinders
---------
Disk /dev/sdb: 486300cyl
Sector size (logical/physical): 512B/512B
BIOS cylinder,head,sector geometry: 486300,255,63.  Each cylinder is 8225kB.
Partition Table: gpt

Number  Start  End        Size       File system  Name  Flags
 1      0cyl   486299cyl  486299cyl  xfs

-----------------------
cylinders/heads/sectors
-----------------------
Disk /dev/sdb: 486300,95,2
Sector size (logical/physical): 512B/512B
BIOS cylinder,head,sector geometry: 486300,255,63.  Each cylinder is 8225kB.
Partition Table: gpt

Number  Start  End            File system  Name  Flags
 1      0,1,0  486299,254,57  xfs

---------
fdisk x p
---------

Disk /dev/sdb: 255 heads, 63 sectors, 486300 cylinders

Nr AF  Hd Sec  Cyl  Hd Sec  Cyl     Start      Size ID
 1 00   0   1    0 254  63 1023          1 4294967295 ee
 2 00   0   0    0   0   0    0          0          0 00
 3 00   0   0    0   0   0    0          0          0 00
 4 00   0   0    0   0   0    0          0          0 00


Unfortunately I'm really crushed with work right now (catching up on all the
lost hours over the past couple days) but my hope is that a little later this
week I can make a second copy of the drive contents then see if I can
recreate the problem. It's not going to be highly scientific or anything, but
 I'm hoping that within the space of 15-20 minutes I can recreate the problem
and post back some definite steps to cause the problem again.

At least, I *hope* I can recreate the problem. I'll actually be a lot more
worried if I can't.

Cheers,
Kevin W.