Disk layout for XO-1.5

Paul Fox pgf at laptop.org
Mon Jul 27 19:42:04 EDT 2009

mitch wrote:
 > 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

i would normally balk at such a large root partition, but if
we're planning on using the olpc-update symlink farm mechanism
for updates, then i think we'll be glad we have it.  (i do think
we need to make sure we're not squandering space needlessly --
the current 1.1G seems large, even accounting for it being
uncompressed, and holding two desktops.)


 > /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.
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 > Devel at lists.laptop.org
 > http://lists.laptop.org/listinfo/devel

 paul fox, pgf at laptop.org

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