[Nook Color Q&A, Help & Troubleshooting] DeanGibson:
After my intentional repartitioning at a B&N store (see above), I decided to try to find out what would happen (eg, where B&N would store downloaded books/etc) as one started to run out of space in the new 5GB "B&N storage" (/data) partition.

It turns out that the above was not an especially good idea ...

In the /data/local folder, I used:

busybox dd if=/dev/zero of=space1 bs=1024 count=1M

to create a 1GB file. I repeated this with different filenames to mostly fill up the partition, until there was about 300MB of available space, while my 1GB "user storage" was virtually completely empty. Of course there was a "low memory" warning on the NC (a small icon in the notification area).

I then unarchived my B&N purchases, and the documents reloaded into the "B&N storage" area, even with the "low memory" warning.

So, I continued to fill up "B&N storage"﻿﻿ until only 3MB was available. I thought that would be a good test, since my B&N books are both larger than that.

I never got to find out where the B&N books would go, because the system became very erratic (eg, the library would not load, nor would some Android Market apps). Further, the system cleared the WiFi configuration file (probably when it tried to rewrite it, as it does when it makes a connection). As a result, the NC (rooted) was completely unusable. Whether this would happen in the normal case of installing apps and books/etc, I don't know. From my previous message above, the system seemed to work OK with about 300MB of space left in "B&N storage"﻿﻿﻿. What the Nook does with downloads as the space gets tighter, we don't know. We do know that even after it is giving a "low memory" warning, it will continue to download books. Perhaps there is a check before the system goes "critical" ... I hope so.

I need to point out here that the above situation was the good news.

The bad news is that when I tried to restore (using ClockworkRecovery) my backup of 1.2 (repartitioned), it would not restore to the "B&N storage"﻿ (/data) partition. Even when I reformatted the partition using Android tools (see below for the mess that became), I could not get ClockworkRecovery﻿ to restore to /data. To be specific, when ClockworkRecovery﻿ does a restore, it does a format first, and it was the filesystem format that was failing.

So, I said to myself, "what's different?" What's different is that the "new" "B&N storage"﻿ (/data) partition﻿ is over 4GB.

So, I said to myself, "I think it's time to try going back to a 1GB "B&N storage" (/data) partition﻿."

So, I booted Honeycomb v0.4 from an existing SDcard. Only problem is, the partition formatting tools on Honeycomb﻿ are not adequate (the required programs are not even there in "busybox") to format either the Linux ext3 partitions or the Windows FAT32 partition !?!?!?!

Fortunately, I had rooted 1.2, and those tools were still on the NC's /system partition (which fortunately doesn't need to be moved as part of the repartitioning process).

So, after proceeding very carefully, I repartitioned my NC to the old B&N sizes, and reformatted /data (0p6/ext3), /cache (0p7/ext3) and /media (0p8/vfat). Then, I attempted to restore my last backup of 1.2/repartitioned. Fortunately, while the terminology (and the file extensions) for the backups imply that those are "image" backups, they are not; they are filesystem backups:

An image backup is an exact disk image of a partition, which captures all data (including deleted files, etc) into an image file that can (with rare exceptions) only be restored to the exact same size partition.

A filesystem backup is just that; a backup of every directory and file in the partition. Such a backup can be restored to any partition of sufficient size.

Now for the really good news (some four hours later):

The restore of my "B&N storage" /data partition into a 1GB partition worked.

When I un-archived my B&N documents, they went into the 5GB partition, just like before the B&N repartitioning. This means that what I did above, can be done on any "B&N repartitioned" NC. That's good news!

The only bad news is that ClockworkRecovery (3.0.2.8) cannot restore data to a partition that is bigger than 4GB. [Edit: 2GB] ... Sufficient to say, while this is not B&N's fault, I think it's a very good reason not to go with the B&N repartitioning.