[Verizon Galaxy Note 3 Q&A, Help & Troubleshooting] bftb0:
Safestrap uses a couple of mounting tricks where the non-stock slots are just giant files stored in the p25 partition (the /data mount point of the so-called "stock" slot). It absolutely does not re-partition the device.

That has a couple of implications.

The first one is that available flash memory space disappears from the stock slot just as soon as you create a non-stock slot - you just created a couple of giant (but empty) files. Even though you might not have installed a ROM in there (yet), you have used up file space "in the stock slot".

If you are booted into a non-stock slot, you will see those giant file blobs underneath the /ss mount point.

(they are somewhere under /data if you are booted into the stock slot or in the recovery - perhaps /data/media/ss. I can't remember right now). Don't touch them unless you are absolutely sure you know what you are doing - manage them using the Safestrap recovery, not external tools (if you can avoid it).

The second implication is that because the size of those blobs is fixed when you create them, they don't expand or contract depending on usage. You are stuck with that size*.

Third, it is quite correct behavior for whatever ROM you have booted in a non-stock slot to report free space remaining inside those file blobs because that's exactly how much you have inside the container the currently-booted ROM is operating in. It does not make sense to report the free space of the outer container**. Safestrap works by "fooling" the ROM to believe that there is nothing unusual going on.

Fourth, there is something important for everybody who uses Safestrap to understand: because those blob files are just normal files inside the p25 (or "stock slot /data mount point") partition, the stock slot /data filesystem needs to be able to mount correctly so that the blob files can be loopback mounted. (It gets mounted somewhere else instead of /data by the Safestrap trickery when you are using a non-stock slot). That means that - dog forbid - if the stock slot /data partition files system ever gets corrupted so that it will not mount - you will simultaneously lose the ability to boot ANY ROM on the phone. Or get access to your backups if you have not put them on an external SD card. You will be forced to re-install pure stock using Odin/Kies, and re-root the phone if you do not keep a good nandroid backup on external storage***

Even the Safestrap "recovery" (which is not a recovery at all) is engineered so that a ROM file containing a boot partition will appear to flash correctly, but what actually happens is that the bits for the "boot" partition are sent to /dev/null - All Safestrap ROMs are booting off the stock kernel and stock ramdisk.

Hope some of this rambling helped. Footnotes below.

* Deleting unused slots will free up space in the stock slot. And you can change the size of non-stock slots, but only by:

- make a nandroid backup

- delete the rom slot (using Safestrap - don't fiddle with the blobs unless you know exactly what you are doing)

- re-create the rom slot using the size you prefer

- restore the nandroid backup to the newly created slot.

**If you want to find out the size used/available in the "outer container" while booted into a non-stock slot, you can (inside a terminal emulator or using adb) do this:

$ df -k /data

$ df -k /ss

(The first one tells you what the current slot is using out of its total, and the second one will tell you how much is being used in the "outer" container).

*** So, get your nandroid backups onto external storage. Technically speaking, the "recovery" portion of Safestrap lives inside the /system partition - so it might be possible to rebuild the stock slot if you made and kept a Nandroid backup of the stock slot and copied it to external storage. If you don't do that, it's "start from square one" time for you Odin/re-rooting/etc. Note also that if you used Kingo to root, and that site has gone down in the meantime, you will be back to pure stock with no ability to restore your custom ROMs. (That's the downside of using an "online" rooting method - you can't back it up for a rainy day.)

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---------- Post added at 09:50 AM ---------- Previous post was at 09:11 AM ----------

If folks want to put dev ROMs in their stock slot, that's their decision.

But I will make a recommendation that seems to be missing from those howto threads:

Using Safestrap's recovery, make a Nandroid backup of the stock slot while it still has "lightly rooted stock" installed, name it so that it will be easily identifiable in the future, and get a copy of it off of the phone for safe keeping

You may never use it. But when you suddenly have a need for it, you will know exactly why you did this. One of those "hear me now und believe me later" deals. ;)