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Root Confused after swapping sdcard and sdcard_ext in vold.fstab


Android Expert
Nov 15, 2009
Central NJ
My son has a rooted stock Droid X2 and he pushes it/me to the limit with the number of bulky games he installs. As you've probably guessed, he often runs out of space. I've managed to alleviate the problem a few times by using Titanium Backup to integrate system app updates into the ROM, or by moving apps to the "media area". Having used those tricks to their fullest, and seeing that his 2GB external sdcard was not being used, I found a few threads indicating how easy it is to swap the internal and external sdcards with minor changes to vold.fstab, replaced the 2GB card with a 16GB card, and made the swap, copying EVERYTHING from the internal to the external immediately prior to the swap. The only app issue I observed was that Google Drive would crash when opened. Removing and re-installing the app fixed that issue. One other issue is that the phone reboots when connected to a PC in mass storage mode.

Subsequently trying to free up some space for installing yet more apps, I used Titanium Backup to identify the space hogs, and moved two of them to "SD card" (TiBu terminology, but I think it refers to /sdcard), only to have Android tell me that I'm running low on space on my "SD card" (Android terminology, but I think it refers to /sdcard_ext). Using the native Android application manager yielded the same results.

Contributing to my confusion are the multiple names by which these locations are referred, including "internal", "sd card", "media area", "sdcard", "sdcard_ext", etc. - enough to give me a headache.

To me it appears that moving apps to the "SD card" (TiBu) or "media area" (native app manager) actually moves the app (but not the data?) to the 4GB built-in memory, regardless of how it's mounted or what changes I've made to vold.fstab. Is that what's happening? Can anyone help explain further, or correct me?
After quite a while of restoring apps one-by-one and moving them to the "sd card" (TiBu), I told TiBu to move remaining user apps to the sd card and went to bed. The next morning the phone would reboot about 1-2 minutes after the initial display of the lock screen.

I ended up doing a factory reset, wiping the 4GB built-in memory (now mounted as sdcard-ext). After restoring many apps one-by-one and moving them to the sdcard, Idiscovered that Android (at least 2.3.5) has a limit of 123 apps on the sdcard. After restoring everything, including system settings, the phone began the reboot issue again.

Another factory reset later, I've got about 65 of the largest apps on the sdcard, DID NOT restore system settings, and everything seems fine, except that the phone/touchscreen seems somewhat less responsive when charging.

What I've learned:
  1. Swapping the mounting of "/sdcard" and "/sdcard-ext" has no effect on where apps end up when moved to the "Media Area" (under Application Management) - they still go to the built-in non-removable 4GB storage area, and it therefore doesn't change the space available for "Media Area" app storage
  2. Android 2.3.5 has a limit of 123 apps in the "Media Area"
  3. Swapping the mount locations CAN help a lot if you use apps that store a large amount of external data. This is because under a stock configuration, the mount point "/sdcard" is the same as the "Media Area", and if you move apps to the "Media Area" you are reducing the space available on "/sdcard". By swapping the mount points, you're separating these two areas, giving you a 4GB "Media Area" for app storage, and 16GB (size is up to you) area for external app data (like downloaded GPS maps, or in my son's case, Modern Combat 3 data).

By doing the swap, and replacing his (unused) 2GB removable card with a 16GB removable card I was able to:
  1. make over 10GB of space available on "/sdcard", which was previously full
  2. move more, larger apps to "Media Area", freeing up 600MB of internal app storage area (under Settings > Storage), and making 2.5GB more space available in "Media Area"

Though it was a lot of work, I learned a lot, and could do it much quick now, and I managed to prolong the life of the Droid X2. It's not that he or I LOVE the phone (though I think it's pretty good), it's that it's the phone he has, and it's pretty much the best non-LTE Verizon phone I know of, and since he's using Page Plus, that makes it a keeper.
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