[SOLVED] Samsung Data Migration "An error occurred while writing to the Target Disk" 301001

Make sure your source drive is Disk 1 and target is Disk 2 (whether that is forced via physical connections or configured in your BIOS) -- please leave feedback if there is a better way to articulate this answer!

Read on below for more details if you need them...

Today I was required to clone a Samsung 840 EVO SSD that has been intermittently failing ever-increasingly in the past couple of weeks.  My new drive is an 850 EVO.

I connected the 850 EVO via a Thermaltake USB 3.0 dock.

The Samsung Data Migration software happily detected both drives (although the software listed my 840 EVO as a "Generic- Compact Flash USB device"), but when I started the clone, after about 8 seconds, the software stopped with the following error:

"An error occurred while writing to the Target Disk"
(with the error code 301001)
Perplexed because it detected the drives fine, I began investigating.

After playing around with a few ideas, I had the thought that maybe it didn't like the fact that I was plugged into an external dock.

Unfortunately I didn't have any extra cables, so I had to unplug a secondary internal drive to be able to plug my 850 EVO in.  This worked like a champ and I'm about 46% finished cloning as I'm writing this.

I began writing this with the intent to tell my readers that you need to plug it in to the internal and not use an external adapter.  However, with further investigation, I discovered the following in Samsung's Data Migration Software manual (English - other languages here) under "Limitations" on page 5 of the PDF:
#5. "On systems with two(2) drives of more (e.g. "C:", "D:", and "E:" drives) with the operating system installed on the "C:" drive, only the first two drives will be cloned.  The "System" partition that is created during Windows installation is automatically replicated.
Now I may have read this incorrectly, but it suggests to me that you need the Source disk as your first HD and the Target as your 2nd (whether that's configured through plugging into the correct ports on your motherboard or set in your BIOS I am not certain at this time) for this to work.

I think it worked for me because I limited myself to the two SATA drives so there would be no confusion (though that only happened because I needed to use the storage drive's SATA cable and power.  LOL

I would love to hear from you if you have had a similar situation... especially if you kept more than two drives connected and/or if you successfully used a USB/SSD dock/adapter.  I would imagine those with thin laptops that can't connect a second drive would need that to work.

I hope this helps save someone some time!