Disk layout for XO-1.5

[Mitch Bradley]

This is a request for comments on a proposed disk layout for XO-1.5.

XO-1.5 will have "managed NAND" instead of raw NAND, so we can use 
conventional filesystems instead of e.g. JFFS2.

Proposal:

The internal NAND storage will be partitioned with an FDISK partition 
map, into three partitions:

/boot - 50 MB - FAT16
    Contains olpc.fth, vmlinuz, initrd, and any other files that OFW 
needs to access during booting

/ - 2 GB - ext4
    Contains system files

/home - remainder of storage - ext4
    Contains user files

Dual-boot systems might have additional partitions for Windows.  That 
will probably require storage devices > 4GB.

The partitions will be aligned to at least 1 MiB boundaries, ensuring 
that they do not split internal NAND erase blocks.

The choice of FAT for /boot makes it usable for both Linux and Windows.  
The choice of FAT16 avoids any possible patent issues surrounding 
FAT32.  FAT16 works fine for 50 MB partitions, using a 1K cluster size.  
With larger cluster sizes, there are several factors of two of headroom 
- and large clusters are not a problem for /boot, which tends to contain 
mostly large files.