Geebox' free up memory thread -- read before attempting

[Guest dwallersv]

geebox posted a thread about how to free up about 17MB in Main Storage, and for some reason it was closed. I'm not sure, but maybe this is why:

Replacing ROM files with zero-length dummy replacements does not actually free up any space in Main Storage, so these changes will not only not recover storage space, they will also take away functionality unnecessarily.

I think geebox is mistakenly comparing a tool's assessment of total space usage with ROM files included, in the before and after scenario, than with this option turned off (in Memmaid, or SK Tools, etc.). This will make it appear that replacing a ROM file with some size with a size 0 dummy results in less total space usage, because the ROM file, and its size, is then hidden by the normal directory traversal interfaces. Result: Calculation appears to show less space used than before.

However, this is deceptive, because no space has been recovered in the user-accessible Main Storage. In fact, a tiny bit of space in the way of directory tables and other filesystem structures has actually been consumed. In order to make the correct apples/apples comparison, to determine impact on user-accessible space, including ROM files in usage calculations must be turned off.

A way to see this paradox is to replace any large ROM file with a dummy that is, say, half its size. Before doing it, check total space usage with, and without ROM files included. Then, replace the file with the smaller one, and repeat the measurements.

What you will find is that space with ROM files included in the calculation will appear to have decreased by the amount that the replacement file is smaller, but with ROM files not included, space calculations will show that usage has increased by the size of the replacement file!

The latter calculation is the real one. When you replace a ROM file, that file is stored in user-accessible Main Storage, and file-system structures are adjusted to point to the new location, even though the name is the same.

As for ROM files "coming back": No need to hard reset. Simply delete the replacement file of the same name, reboot, and voila! The ROM file is back.

Bottom line: There is nothing to be gained by trying to eliminate ROM files. They are not stored in Main Memory, so over-writing them with something smaller doesn't save any space at all. It's an illusion.

Sorry for starting a whole thread about this, but I couldn't post it as a response in the locked thread.

Edited December 20, 2009 by dwallersv

[Guest nap_rz]

why would anyone be bothered with doing such complex task to free up 17MB from a 8GB internal storage? and you could always buy a micro SD card if you need more storage.

Edited December 20, 2009 by nap_rz

[Guest Uboy]

why would anyone be bothered with doing such complex task to free up 17MB from a 8GB internal storage? and you could always buy a micro SD card if you need more storage.

Not Internal Storage or My Storage as it is on my phone but Storage Memory, which out of 150.5MB available in total I have 10MB left, so I don't see why replacing large un-used files in Storage Memory with small un-used files won't free up some Storage Memory. Of course it can't free up any ram. ;)

[Guest dwallersv]

Not Internal Storage or My Storage as it is on my phone but Storage Memory, which out of 150.5MB available in total I have 10MB left, so I don't see why replacing large un-used files in Storage Memory with small un-used files won't free up some Storage Memory. Of course it can't free up any ram. ;)

Read the OP, Poindexter. ;)

[Guest Uboy]

Read the OP, Poindexter. ;)

Read it, twice now, I was under the impression that rom files were stored in the inaccessible part of the storage memory and copied to the usable partition on first boot. I have replaced many files in my windows folder, I always thought that the original ones were overwritten.

[Guest dwallersv]

Read it, twice now, I was under the impression that rom files were stored in the inaccessible part of the storage memory and copied to the usable partition on first boot. I have replaced many files in my windows folder, I always thought that the original ones were overwritten.

That's the error.

ROM files are not copied to user-accessible storage. Windows Mobile has special features implemented in the filesystem driver to manage this "dual" access to ROM and to NVRAM. It "knows" where a file is located, and simply manipulates filesystem pointers (like references in directory structures) as necessary.

So, ROM acts kind of like a "shadow" filesystem. This data is accessed directly from ROM, not copied into precious NVRAM. When any file in this "shadow" FS is overwritten, the new file data does, of course, reside in NVRAM, and the pointers in the FS are adjusted accordingly.

It gets even more interesting. You can rename a ROM file, and it will take on that new name, but still not be copied to NVRAM -- again, the only changes are to the filesystem tables, where filenames are stored.

The filesystem structures are stored in NVRAM, and this is where all the magic happens.

Bottom line: There is no way to "recover" file space from ROM files, other than to cook a ROM and remove them, then flash the new ROM on the device. The term "ROM" is even inaccurate these days and archaic, because the actual device memory in question is really either EEPROM, or quite often, just a partition of a single NVRAM for which the other partitions(s) includes the Main Storage. IIRC, the latter is the situation on the Omnia and O2. Tends to be the clower cost solution these days with the price of memory so cheap, leaving the distinction between "ROM" and "Storage" being entirely artificial, managed by and enforced purely by software (the FS driver).

[Guest Uboy]

Thanks for the clarification, I stand corrected ;)

Edited December 20, 2009 by Uboy

[Guest geebox]

Thanks for the clarification, I stand corrected ;)

Yeah my program expert friend says that my mod is an illusion and that nothing will change as far as true memory gain. He said I must have did something else to get my numbers, Hmm now I got play round and see what I did to get my so called free memory back to 48mb