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Root new SD card

Lecture time! :D
We're talking about the file systems computers use to store data. Every operating system (our beloved Android included) has to have a method of finding all those ones and zeros on your device, cards, and drives. There are a great many file systems out there, but not all are created equally. A file system is made of two or three parts. The first part is a File Allocation Table (thats where FAT comes from), which is like the table of contents for a book. It tells the computer where the ones and and zeros are that make up your file. Second you have "clusters" which are easier to think of as storage boxes. This is where the FAT points to. Third, you have the journal. More advanced file systems have this to make house keeping easier and to make your data harder to lose in the event you have a major problem. The journal is like a running tally of whats going on with the file system as it's happening.

Now we've covered the terminology, here are the file systems you are likely to encounter in your day to day life:
FAT 16 = DOS, Windows 3x, 95, 98, etc. This is the oldest one still in common use.
FAT 32 = Windows 98 and up. Based on fat 16, but with smaller clusters for more efficient use of space. Almost every SD card in the world uses this.
NTFS = Windows NT, 2000, XP, Vista, & 7. More secure and efficient than fat based file systems, includes permissions, and a journal.
HFS = Mac OS (up to OSX) Much like NTFS, but all Steve Jobsified.
EXT2,3,4 = Unix, Linux, OSX, Android. Again much like NTFS, but with progressively smaller clusters. Also Journaled.

The clusters are block of space on the drive, and each can only be allocated to one file. If you have a text file that is 17KB on a FAT16 drive, it will take two clusters (each holds 16) therefore you have 15KB of wasted space. The same file on an NTFS drive (4KB clusters) it will take 5 clusters with only 3KB of wasted space. This wasted space is called file system overhead.

So now you can see, there are huge benefits of choosing one file system over another. FAT32 isn't terribly efficient, but it can be read by just about every device still functioning in the world, so it's hugely compatible. EXT(2,3,or 4) is a great choice for systems that can read it, but can't be seen natively by Microsoft based systems, meaning no USB storage options. Also, there are two I didn't go into, FAT12 which is for floppies, and RFS. RFS is a another Linux type, not hugely supported, but the default file system for some Android devices (like the Intercept). File systems tend to be backwards compatible, i.e. a system that can read FAT32 can also use FAT16, etc.

Read chapters 16 and 17 of your books, and remember to study! The test is this Friday.



You can tell I used to teach this stuff, can't you? ;)
 
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Link2SD works best (fastest) on an EXT partition. That's why my card has 14GB FAT32, 1.2GB EXT4. The missing 800MB is filesystem overhead. If that seems like a lot, remember that it's cumulative. The larger the drive, the greater the discrepancy.

@cammy - If you feel like reposting any of my "lectures", feel free, just give me credit. What use is knowledge not shared?
 
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