Before I get into the thick of this, I've been for a little over a week or maybe even more taking as much time as I can to explain to people what MTD is and the risks of it. And unfortunately most people just by natural human tendencies have an issue comprehending it which believe me is perfectly fine haha, it's a lot to take at once. So I'm going to layout the basic need to knows, and if any more information is needed feel free to pm me and I'll add it into this main post.
I'm going to try to make this as simplistic as I can.:x
What is a partition?
A partition is an area of allocated space, a division of the whole overall area of space. In this case our partitions on the Epic 4G are /System, /Data, as well as /Cache. All with set permanent sizes.
What is a partition map?
A partition map is the configuration of our partitions, it's what in a vagueness sets our required sizes for the divisions of our nand also known as flash memory. A partition or partition map should not be confused with a file system. An example would be BML and MTD.
What is a file system?
A file system resides on the partition map and governs the data being read/wrote/moved/etc by the Operating System, in this case Android. Changing a file system is less complex than an overall change in partition mapping. They again, are not the same thing.
What is MTD?
MTD is an Open Source Partition map. It allows those who are using it control over how their partitions are sized and how much space is allocated here and how much space is taken away from there. Currently on MTD we have 689 megabytes of space allocated to our /data partition allowing more to be downloaded from the market as an example. MTD as a partition config has YAFFS2 as a file system residing on it governing how data is transferred and the speed of which it is done. EXT2 through 4 aren't possible on the MTD platform, just as YAFFS2 may not be possible on the BML proprietary platform.
What is BML?
BML like MTD is a partition map, however it is proprietary in nature, Close Source if you will. The size for /System /Data /Cache is set and permanent and makes opening up space more of a task for Developers. Stock the Epic 4G comes on BML, and is running RFS as it's file system, once rooted you can leave RFS for EXT4 (Journaled or Un-Journaled) as long as the kernel you use allows for EXT4. But in the end, changing a file system on BML does not lessen or enhance the control you have over your partitions.
What do I need to know before flashing a rom with this?
Currently there are two distributions which have moved over to the MTD platform.
One of which and the first inital one being:
[ROM] Epicmtd CM7 SELFKANG (12/10) - 2.3.7
And the second which is a basis of the first:
[ACS] [MTD] [YAFFS2] MIUI 1.12.2 Beta 6 MTD (Updated 12/10/2011)
Within the flashable zips for these two roms there are scripts which completely format your device and move you to MTD. It is required to back up the things you wish to keep with Titanium backup if you have it. Nandroids from RFS/EXT4/BML do not work on MTD/YAFFS2. Alternatively if you have purchased appextractor or titanium back up pro licensing from the Android market you can make a nandroid before your move and then extract the data apps or system apps you want from that backup while on MTD/YAFFS2 without going into recovery.
When flashing one of these ROMS in CWM5 your phone shall reboot during the installation if it finds you're on BML, don't panic it is a natural process of this move.
When booting into recovery on MTD it reacts to how long you hold the 3 button combination. Being Volume down, Camera, and Power. Don't panic if it doesn't pop up, you must let go to let it know which path it goes to. If your phone looks like it's booting again don't do the combination. It's switching from the init to the recovery.
CWM 5 is not broken, on MTD our kernel now has a 2 stage init. And it's part of the process.
How do I go about flashing other roms if they're not MTD?
Flashing a Stock TouchWiz rom can be very problematic, mainly due to the nature of and differences between MTD and BML. Currently there isn't a stock MTD kernel. To return to BML, you have a choice of either using Heimdall or Odin. To do so you require the victory.pit as well as a stock tar of your choice which includes our bootloader so that when you repartition your device all goes well without problem. There is no method to return without using Odin/Heimdall because BML is a proprietary configuration. We lack the tools to replicate Samsung's methods and mannerisms.
What does it mean for me as an end user?
As an End User, MTD is an opening to a new life for the Epic 4G. Things like ICS, more space in data or system, are more within our reach and grasp due to the nature of Open Source MTD is immersed in. We're closer to the Captivate, Fascinate, Vibrant, and Galaxy S international by being on MTD, we've that new freedom they've had for a long time. Not to say things like ICS aren't possible on BML but with this we're at a better standing point.
Stock EI22 on MTD
noobnl as well as Tortel have worked together to put a stock EI22 rom for the MTD platform which can be found here.
[EI22] Stock-ish MTD Build
This is for a stock experience and for those want to use MTD as well as make use of the stock features our phone has, nothing out of the ordinary or custom, just as a basic point. Rom Developers can go on towards moving their roms over to this platform now with the use of the boot.img but for now kernel developers will still have an issue nonetheless.
Those responsible for this in no specific order: Decad3nce, noobnl, jt1134, mkasick, nullghost, nubecoder, DRockstar, UberPinguin, Rodderik, wtogami, as well as countless others.
All things within this thread are subject to change if a need for correction is to be met.