[Samsung Galaxy Mini] Doc_cheilvenerdi.org:
Interesting Questions about "Internal Memory to SD" Hack!

Is this tweak safe?

Looking to data safety this tweak uses an ext4 filesystem. I choosed a journaled filesystem just to avoid data loss or data corruption during the daily usage. This doesn't mean that you have an invincible filesystem, simply it's really more difficult to loose them in an unpredictable way...

This benefit granted by the user has an immediate impact on filesystem performance... I need time to keep update the journal while using the filesystem...

We can say slower but safer then...

Otherwise, looking to SD Lifecycle, a journaled filesystem write more infos toghether with data onto the device... Actually, if a standard SD Card has a write lifecicle certified for 10 milions write operations, we could shorten it's life using in this more aggressive way...

When I tried first this tweak and decided to share it, I compared the SD lifecicle and it's Market price against Internal Phone Memory lifetime (One hundred milions write operations long) and I prefer to loose performance and to shorten SD lifetime against the benefits that I gain in the daily usage: more memory available; possibility to exchange SDCards while testing different data configurations, easy backups from PC side and so on...

P.S. Actually I'm testing a system configuration (...still too far from user friendliness...) with the whole Android on SD card... This extreme tweak lets me change firmware simply changing SDCard on reboot... I cannot brick the phone anymore while I don't need to flash anything else anymore... I can test/mod/backup/restore everything in a really easy way... and so on...

Finally I'm balancing between "safety against data loss" and safety as "SDcard lifetime", leaving aside "performance" for a while... I choosed the first one trying to reduce the second one a lot...

If you compare my boot sequence to other known custom ones, I decided NOT to check the ext4 filesystem for errors on any device boot, but left the user free to do it when needed: I wrote a free application to do it (EXT4 Checkup); you can launch it once a month or when needed without checking any day during any phone boot...

I can also suggest you to read this thread: [TOOLS + HOW TO] Disable and enable journaling in internal ext4 Partitions.

They talk about removing the journal from the ext4 filesystem... this hack surely gains performance and reduces write operations on the SD Card, but could be dangerous against data safety... you should use it - for example - with an SD card where you have games or apps which don't need backups...

I repeat: Read the thread Carefully! It's a topic to really understand before trying it!

After reboot it takes long time to scan SD for multimedia files; is it normal?

In Italy we call the boot process of the phone a Bottleneck:

when the system boots, many services are started alltogether with asynchronous tasks and many backgrounded applications query for their data and write new infos... everyone on his own...

This means that during the first boot stage many (really many) read/write requests to and from the /data filesystem will be performed with multitasking questions but will be executed with ordered sequential tasks due to hardware SD technology... The hardware device simply put all the read/write requests in a single queue...

Finally, during first boot stage, Android query the first FAT32 partition too, searching for multimedia files...

...sigh... using the same single SDCard device queue...

...now the answer is simple too: On first boot it's normal - using this tweak - that the multimedia scan is slower then the original one: Here I have FAT32 and EXT4 on the same queue (heavy filled up on boot) while in the original system I find one queue for the SD FAT32 and another one (different hardware device) for the RFS /data filesystem...

Once booted, it will be difficult to find many services querying alltogether for filesystem and/or FAT32 partition.

P.S. Filling the FAT32 partition with multimedia files slow down any Android anyway... when scanning for one or more thousand movies, songs and photos, I don't bet on performance...

It takes more time to scan SD, if compared to other tweaks; is it normal?

This tweak moves the full /data partition to the SDCard but doesn't change the FAT32 one, so no differences should occurr when the phone is up and running... the difference could be noticeable, instead, while booting... as explained above...