[EVO 4G Original Development] mhwarfield:
Well, it is and it isn't. The data partition is still where it was (unless you use "a2sd xdata" to bind mount all of /data) but there are a number of subdirectories which are bind mounted to /sd-ext which is different. Some data directories remain on the data partition while the big ones get bind mounted over to the sd-ext partition. The /data/data, /data/app-private, /data/app-asec, and /data/data are bind mounted over to /sd-ext but not everything on /sd-ext is visible in /data, which presents another problem... But /data/backup does not get bind mounted over and remains on the original data partition. So, quite literally data != sd-ext.

localhost / # df /data

Filesystem 1K-blocks Used Available Use% Mounted on

/dev/block/mtdblock6 437888 147964 289924 34% /data

localhost / # df /data/app

Filesystem 1K-blocks Used Available Use% Mounted on

/dev/block/mmcblk0p2 30408732 732880 28131148 3% /sd-ext

localhost / # df /data/backup

Filesystem 1K-blocks Used Available Use% Mounted on

/dev/block/mtdblock6 437888 147988 289900 34% /data

So, perhaps it would have been more correct on my part to not say he was incorrect but that the use of the unadorned term "data" is ambiguous in that it does not, in this (his) case, refer to the partition that is mounted on the /data directory where a large number of directories exist. But... In recovery, when you "wipe data" it's that partition that gets wiped so, in recovery, "data" does mean the partition that mounts to "/data" and not the one on /sd-ext hence the abiguity.

At one point, I was also using /sd-ext to archive some overflow from /sdcard. When I first started playing with this rom (which preceeded that article he pointed to) I ran into some fsck errors that a2sd could not handle and I used "a2sd formatext" to just wipe and fix it. Fortunately, I had backed up that partition to my computer previously because, obviously, that loses everything on that partition whether it's mapped over to data or not.

I wasn't aware that the sd-ext partition was for the exclusive use of a2sd and could be / should be wiped in the case of a fresh ROM install like that. That's not good. I would have made that partition a LOT smaller, had I known that. Right now, with about 200 apps on that phone, the sd-ext partition is only running about 3% full and, if there's a non-neglible chance it may have to get wiped in the future, I can't use any of that space for anything else, even outside of the data bind-mounted directories. I guess, now that I know this, I really should repartition that down much smaller to recover all that wasted space.

Now realizing all that, I went back to the Amon_RA recovery and looked at the combo wipes. Now I see what the difference is. Even the superwipe will not fix this problem. That's (B,C,D,S)*3 which wipes "Boot", "Cache", "Data" (and that would be /data) and "System". It was the factory data reset which does the D,C,A,E which takes out the "SD-EXT" partition. So, it was when I ran the factory data reset after running the superwipe that really fixed the problem and Amon_RA is very clear that "data" != "sd-ext". We should probably be more careful about using precise, consistent, terminology, myself included.