Thread: Booting from MMC on N800 Now Available!!
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freeman is offline freeman
2007-02-20 , 03:45
Posts: 152 | Thanked: 6 times | Joined on Dec 2006
#69
Originally Posted by DCr33P View Post
Why should there be at least one FAT partition on the mmc/sd card when booting from it? Ext2 is the boot partition with rootfs, so what's the FAT partition for?
The fat partition is to store data, well at least data that used by the application that nokia made, stuff like contact, backup, etc. Which make good sense, because in windows world, FAT is the best compatibility FS between all OSes. It make things a lots easier to move data around between Windows&Linux&n800.
Originally Posted by DCr33P View Post
The second interrogation mark in my head is the wear issue. Jffs2 uses wear leveling to harmonize the write cycles throughout the jffs2 partition. So if we have a 512 mb parition, we have to commit about 50tb of traffic (512 * 10^-6*100000) to reach the 100k cycles limit. By the time we reach this amount there should be Nokia Internet Tablet OS 2280, so that's not a problem.
Well, there is no way to predict when the flash will fail or how many write it will take. So, moving the written part to the SD card is better because it's replacable regardless of when or how it fails.
Originally Posted by DCr33P View Post
But what about ext2? If we are unlucky, we can wear out some specific blocks in a few months and had to suffer from read errors. Does the SD Controller have error correction? 2bit errors in one word (does not matter that much wich size, imho) are unlikely and 1bit errors can be corrected easily... Hmmm.. just some thoughts on it.
well, if you like you don't have to use ext2 as a rootfs, you can still use jffs2. The problem is that jffs2 is compressed fs therefore, overhead. You could also make it use other fs also, like ext3 or jfs, but you will have to compile the kernel yourself. The kernel&loader are store on flash, and those things are read-only. The root can be store anywhere.