[Samsung Galaxy Nexus] purpleonyx:
Avoid Having a Wiping Problem

Some time ago, it was posted that TWRP had a wiping problem, but it was never explained beyond that. Folks like myself who ran TWRP, were able to wipe (as far as we could tell), so we never really looked into the issue further.

I started running TWRP some time ago, and came from CWM. For the past couple of months running Sourcery, I had ran into several random issues that I thought were all ROM-related. With the latest version of TWRP, 2.5.0.0, I thought I was having a problem with it, so I installed CWM, along with ROM manager. Upon opening ROM Manager, I noticed it said I had 2 recoveries installed, and thought this was rather odd. Anyhow, I rebooted into recovery and CWM was indeed loaded. I began navigating the directories, and that's when I discovered the /0 directory which contained /0/sdcard. In this directory, were folders and downloads from a long time ago, I'd say about the time when I last ran CWM. I thought to myself, "How the hell did these directories exist if I did complete 100% wipes within TWRP?" and that's when it dawned on me... I had a wiping problem. As you can imagine, I felt dirty, and so did my file system!

Looking back, the signs were all there. When you wipe a file system entirely, it should be clean. Whenever I did a full wipe on TWRP, there were always directories like sys, etc, bin, mnt, and so on. When I did a full wipe on CWM, the only folder left was called clockworkmod. Nothing else existed.

The reason for the /0 folder is for multi-user support that is being included in Android 4.2. If you added additional users, there would be additional incremental directories, /1, /2, /3, etc, each of which would have separate sdcard, data, downloads, and other folders. Now for the real question. Is this the fault of TWRP, or CWM? All this time, I was led to believe that TWRP was superior to CWM, which is the reason I made the switch. But if this were true, then why is it that CWM can see these additional user folders, that TWRP cannot?

Don't take my word for it. Try it yourself and arrive at your own conclusion! Here are a couple of methods of checking this.

Non-destructive: Flash CWM recovery over top of TWRP. Go into the /0 folder and check the timestamps of files. A great place to check is in your /0/downloads (or perhaps it was /0/sdcard/downloads) folder. If they are old, you have a problem. Boot back into Android. You can easily use Goo Manager to restore your (TWRP) recovery if you wish, or flash a new recovery via ADB.

Destructive: Reboot into recovery (TWRP), and do a complete wipe of everything. Data, system, etc. Blow it all out. There are 2 buttons on the latest version of TWRP for formatting. You want to run both of them. One of the options to format Data, will require you to type in 'yes'. Once you do this, how many directories do you see? At this point, if you choose to require even more evidence, you can use ADB to flash CWM, and you will see even more evidence, that the /0 directory still exists, along with several files if you once used CWM in the past.

I hope this write-up helps others to understand the issues with TWRP's wiping problem. I'm happy to report that nearly all of the random issues I had been experiencing, since JBSourcery 4.x, have been eliminated, and my phone runs much smoother. At the time of this writing, 5.2 now runs amazing for me since I've corrected this issue.

Cheers!