[GUIDE] MTP and PTP (Media Transfer Protocol) vs UMC (Mass Storage Class)

scandiun · Jun 17, 2012

Here I will post the advantages and disadvantages of the two.

Advantages of UMC

UMC works at block level. It means that you access the partition from the operating system like if were local, and you have complete control of it.
For the previous reason, UMC keeps timestamps for files and folders. This is specially important for pictures, photos or videos that don't have EXIF, where you rely on file creation or modification time to arrange them and to know when were taken. MTP sets for all transferred files current system time, thus overwritting the real creation or modification time and ruining your gallery.
UMC allows the use of recovery software (Recuva) or partition software (Easeus Partition Master) and even format with a different filesystem. Without UMC you have to use android side software that usually is less powerful, needs a rooted phone, etc.
As you have total access to the partition, you can access all files there, even hidden, system, etc. With MTP you only have access to the files that the controlling operating system (android) wants. For example, with MTP, files starting with dot (.file) are not accessible. Some file formats are not allowed.
UMC is compatible with any operating system that allows connecting a FAT32 / exFAT pendrive, while MTP requires specific support. Linux and OS X may have built-in support or not.
With UMC you directly access the files, so modification is instant, and viewing. On the other side, with MTP you download it, modify it and re-upload the edited version, but you never do it directly. Even to play files you need to completely download it first. Imagine downloading a 5 GB MKV.
UMC is always the same, while for MTP there are several implementations: MTP, MTPZ (Microsoft Zune), Sony SonicStage, Apple DMAP.
UMC is faster than MTP because requires less time to initialize transfer, but isn't that big difference for an average user. The higher the number of files to be transferred and the lower the size of each file, the higher the ratio MTP/UMC.

Advantages of MTP or PTP

In MTP mode, the android device controls the input/output to the filesystem, so there is no risk of data loss because of cold disconnecting the device from USB. You work on a layer over the filesystem. With UMC you must be careful.
MTP allows you to use the sdcard from both the android phone and the computer at the same time, even to any desired number of them. On the other side, with UMC you only can do it from a device at a time, meaning that you have to unmount the sdcard from the android to view it on the computer, stopping apps, etc. Of course there are software that can force viewing UMC from both sides, but is a highway to corruption.
MTP does not show the native filesystem to the computer (it uses a hierarchery simulated by the MTP driver), so it will always be compatible. For example, on devices with the same partition for data and sdcard (like Galaxy Nexus, Galaxy S3) you are writing from the computer to an ext4 partition and you don't need windows to support it. The same if the device partition were in any imaginable filesystem, the MTP will show you it in a standard hierarchy. On the other side, with UMC your local operating system (windows, linux, mac) must support natively the filesystem of the partition or download some software that allows you to do it.
With MTP you use all capabilities and disadvantages of the device filesystem. If the filesystem is in ext4 you can copy files over 4GB to the device, that you couldn't in UMC mode because usually it will come formatted in FAT32, that is the most compatible fs for all operating systems.
MTP enables Windows Media DRM, UMC doesn't.
MTP allows the use of password for accessing the files (on compatible devices). On the other side, with UMC, of course you could use powerful tools like TrueCrypt, but you need the corresponding software on android that reads it.

How to preserve timestamps

- Use File Timestamp app. Root is required, and works recursively too.
- Use Mass Storage Mode when possible.
- zip or tar the files when sending them to the phone or receiving from.
- If the device has external sd, you can use it as a man in the middle.
- samba (smb protocol) allows preservation of timestamps, however applications for android don't support it.
- FTP allows preservation of timestamps, however applications for android don't support it.
- NFS allows preservation of timestamps, however couldn't get any application for android working properly (Servers Ultimate Pro).
- Rsync allows preservation of timestamps, however couldn't get any application for android working properly (Servers Ultimate Pro).
- adb push and pull does not preserve timestamps. Furthermore doesn't work recursively with folders.
- MTP does not preserve timestamps.
- Cloud services like Google Drive, Dropbox, etc. usually never preserve timestamps.

Questions and answers

Is possible to implement MTP on "put here your device"?

Possibly yes, if has USB. MTP works on software side, so updating your rom or installing a new one will do the job

Is possible to implement UMC on "put here your device"?

That depends on hardware mainly. If the internal sdcard and the data folders belong to the same partition, you can't. The reason is that you can't enable access to a part of a partition at block level, the whole or nothing. This is the case for Galaxy Nexus and Galaxy S3, in order to take advantage of all space, and discard the case where you have filled a partition and the other plenty of space.

Dan Morill said:
It isn't physically possible to support UMS on devices that don't have a dedicated partition for storage (like a removable SD card, or a separate partition like Nexus S.) This is because UMS is a block-level protocol that gives the host PC direct access to the physical blocks on the storage, so that Android cannot have it mounted at the same time.

With the unified storage model we introduced in Honeycomb, we share your full 32GB (or 16GB or whatever) between app data and media data. That is, no more staring sadly at your 5GB free on Nexus S when your internal app data partition has filled up -- it's all one big happy volume.

However the cost is that Android can no longer ever yield up the storage for the host PC to molest directly over USB. Instead we use MTP. On Windows (which the majority of users use), it has built-in MTP support in Explorer that makes it look exactly like a disk. On Linux and Mac it's sadly not as easy, but I have confidence that we'll see some work to make this better.

Sources:
Easy UMS, USB Mass Storage and Media Transfer Protocol – XDA Developer TV
DifferenceBetween: Difference Between MTP and MSC
Directions on Microsoft: What is MTP?
CrackBerry: On startup - Media Transfer Protocol
Ice Cream Sandwich supports USB mass storage after all, Galaxy Nexus does not

Issues and questions:
[Q] Hidden folders through Android MTP
Nexus 4 not showing files via MTP
[Q][MTP] Certain files/directories hidden to windows file manager?
Connecting to PC files are different!
MTP and hidden files
[Q] Hidden files and MTP/Windows
[Q] Do the S3 still using 2gb partition for data and 12 as virtual sd?
Just got meself a Nexus 7... But!
Upload to dropbox: file timestamps should be preserved
Android File Transfer - For Mac users only

filou75 · Jul 2, 2012

Thanks for this guide !

invertedskull · Aug 21, 2012

If I understand this correctly, then devices like the Asus Transformer Eee Pad (TF300T) which has a 16GB or 32GB internal storage, PLUS a microSD card (and standard SD card slot when docked) could use UMC, if the manufacturer made it so (which they haven't), right?

scandiun · Aug 21, 2012

invertedskull said:
If I understand this correctly, then devices like the Asus Transformer Eee Pad (TF300T) which has a 16GB or 32GB internal storage, PLUS a microSD card (and standard SD card slot when docked) could use UMC, if the manufacturer made it so (which they haven't), right?

The UMC should appear then for the microsd, which you can physically remove from the phone, plus the dock if existent.

For the 16/32 GB internal storage it depends if there is a dedicated partition for internal sdcard. Check it for the Eee Pad.

invertedskull · Aug 21, 2012

Well, then I assume(?) Asus were lazy or just didn't think to give us the choice, cos I only have MTP or PTP mode.

I miss UMC.

scandiun · Aug 21, 2012

invertedskull said:
Well, then I assume(?) Asus were lazy or just didn't think to give us the choice, cos I only have MTP or PTP mode. I miss UMC.

Well, assuming that you have your device rooted and with busybox, can you post the output of these three commands

Code:

ls -lR /dev/block

Code:

mount

Code:

su
parted /dev/block/mmcblk0
print

invertedskull · Aug 21, 2012

scandiun said:
Well, assuming that you have your device rooted and with busybox, can you post the output of these three commands...

Sorry, I don't have it rooted. I have been asking around if rooting / unlocking the TF300T would give me the option for UMC, but pretty much everyone told me chances are zip.

scandiun · Aug 21, 2012

invertedskull said:
Sorry, I don't have it rooted. I have been asking around if rooting / unlocking the TF300T would give me the option for UMC, but pretty much everyone told me chances are zip.

Rooting can't change that because it's hardware implemented. You can't do anything about it. Probably the Eee pad transformer doesn't have a dedicated partition for sdcard.

A quick way to check it is see if the free space for the sdcard and the userdata is exactly the same, and is always like that no matter on which of the two partitions you write.

About the issue anyway, modern phones like Galaxy S3, Galaxy Nexus, Galaxy Note and probably newer like Nexus 2 and Note 2 won't have it anymore, it's just the way to go because takes all the advantage of the free space on the device. It will be the standard from now on.

EDITED:

If you want UMS on devices that don't have it, you can use DriveDroid from market (there's both free and paid). With it, create a blank file that will be used as "partition". Then you can connect your phone to your computer and put there the songs you want. Then do the same in the car. For example, in my Nexus 7 I've created a 2 GB file which serve for that purpose (takes a while when is big).

http://xdaforums.com/showpost.php?p=39203658&postcount=21

invertedskull · Aug 21, 2012

I have 20.71GB free internal, and 1.89GB free on the mSD card. :/

scandiun · Aug 21, 2012

invertedskull said:
I have 20.71GB free internal, and 1.89GB free on the mSD card. :/

Because the mSD is another sdcard, different than the internal, in case it has it.

Would be great if you could get the partition scheme as I requested before, or ask for it, to definitely rule it out.

invertedskull · Aug 22, 2012

scandiun said:
Because the mSD is another sdcard, different than the internal, in case it has it.

Would be great if you could get the partition scheme as I requested before, or ask for it, to definitely rule it out.

Is this what you need?

budi5555 · Aug 22, 2012

when i connect my device with computer(MTP conection), i saw 1drive appear, then i go inside, i saw 2drive(iternal&external with how many free space left), go inside again always empty... how to use it?

invertedskull · Aug 22, 2012

I get that also. Just go into either one (internal or external) that you want to copy your files to and do your stuff.

scandiun · Aug 22, 2012

invertedskull said:
Is this what you need?

More or less. The internal sdcard and the external (microsd) are different, one has 27.15 GB and the other 29.80 GB.

Click in the More... and see if you have UMC for the external microsd

invertedskull · Aug 23, 2012

scandiun said:
More or less. The internal sdcard and the external (microsd) are different, one has 27.15 GB and the other 29.80 GB.

Click in the More... and see if you have UMC for the external microsd

Nope, I only have MTP or PTP.

This makes me sad.

WaltA · Sep 4, 2012

Of UMC, MPT, and PTP, which is the most benigh?

I don't know if this is the best place to ask my question, but at least you all seem to understand this all pretty well.

I plug my phone into my PC to just use ADB. Under Gingerbread, I would select "Charge only" as my USB connection type.

With ICS, there is no longer the "Charge Only" option for an USB connection to a PC. I have to pick UMC, MTP, or PTP.

Given I really don't want to use any of those, just ADB, which of the three is the most benign one?

scandiun · Sep 4, 2012

WaltA said:
I don't know if this is the best place to ask my question, but at least you all seem to understand this all pretty well.

I plug my phone into my PC to just use ADB. Under Gingerbread, I would select "Charge only" as my USB connection type.

With ICS, there is no longer the "Charge Only" option for an USB connection to a PC. I have to pick UMC, MTP, or PTP.

Given I really don't want to use any of those, just ADB, which of the three is the most benign one?

Either the MTP or PTP are the safer ones. There is no possibility to select "none" like was possible in previous version as you say. The UMC has the disadvantage that if you activate the Mass Storage usually the /sdcard won't be available from ADB commands.

Anyway, the ADB is separate from those options. The ADB option is usually found under Developer options. You can use adb with any of the options you say.

sniders · Nov 21, 2012

Thanks a lot very very helpfull!

Robertech · Dec 27, 2012

oops, delete post. wrong window lol

PRichardson · Mar 16, 2013

scandiun said:
Rooting can't change that because it's hardware implemented. You can't do anything about it.
...
About the issue anyway, modern phones like Galaxy S3, Galaxy Nexus, Galaxy Note and probably newer like Nexus 2 and Note 2 won't have it anymore, it's just the way to go because takes all the advantage of the free space on the device. It will be the standard from now on.

I thought I would let you (and anyone else reading this thread) know that your post here is wrong. It's not "hardware implemented" in the sense that these two protocols are software implementations of data transfer. In fact, in many cases, even where there is NOT a microSD card that is mounted as a separate partition from system/data, the UMS/MSC (USB Mass Storage Transfer/Mass Storage Class) can still be implemented by this procedure:

1. Root (and optionally flash a custom ROM, that can be easily modded)
2. boot into alt OS, such as Recovery or OS from alt. source (USB OTG?)
3. Partition such that you have the required "separate partition"
4. add kernel modules/libraries you want and will need for UMS/MSC
5. Boot up and enjoy UMS/MSC as well as MTP (if you don't mind crappy speed)

Done.

Also, regarding MTP/PTP (Media Transfer Protocol, which is actually different from Picture Transfer Protocol), being a future replacement for all "modern phones", I am not so sure. It is designed for that indeed, but the Android community is different from most others. I will personally be going out of my way in the future, to ensure all phones I buy have removable uSDcard slots, as long as I can still find them, because it makes recovery in a bind, much easier (like, if there's a problem establishing communications with a computer, and numerous other possibilities). There's nothing like popping in a 32 or 64 Gig card of movies, training videos, eBooks, etc., within 10 to 20 seconds, vice the hours it will typically take to transfer even 5 Gigs of videos over the MTP protocol. Again, I don't like programs handling all my media for me. I prefer to see the files where they live (a higher fidelity simulation, is afterall, a hallmark property of how sharper minds represent reality, and abstractions from it are always mere shortcuts we use in a hurry). You got an easier method to rapidly check file hashes on your phone, from your laptop? Think of it this way, saying that MTP will "replace" UMS, is like saying Apple will replace Linux.

Regards,
Paul

:good:

[GUIDE] MTP and PTP (Media Transfer Protocol) vs UMC (Mass Storage Class)

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