The mount time for a 4G JFFS2 volume will be pretty long. Another problem is that you will use up a lot of kernel memory for JFFS2 internal data structures with a volume that size, assuming that you put a lot of data on it. We have pushed JFFS2 well past its design center with the 512 MiB FLASH. It was really designed for FLASH sizes in the 32-64 MiB range.

I will probably get piled-on for saying this, but in my experience, plain FAT filesystems work well for removable media. FAT was originally designed for removable media (floppy disks), which is not the case for ext2. I routinely use a couple of USB keys to transfer stuff between my host system and OLPC boards. The ext2/3 has needed to be reformatted several times, whereas the FAT one is still using the factory format.

Owen Williams wrote:
So I took a chance and bought a 4 gig SD card
(http://www.newegg.com/product/product.asp?item=N82E16820163159).
I thought it wasn't working...

Dec 6 17:11:10 localhost kernel: mmcblk0: mmc0:b368 SDC 4020224KiB Dec 6 17:11:10 localhost kernel: mmcblk0:<3>mmcblk0: error 1 transferring data
Dec  6 17:11:10 localhost kernel: end_request: I/O error, dev mmcblk0, sector 0
Dec  6 17:11:10 localhost kernel: Buffer I/O error on device mmcblk0, logical 
block 0
Dec  6 17:11:10 localhost kernel:  unable to read partition table

but then I ejected and reinserted and noticed /dev/mmcblk0
and /dev/mmcblk0p1.  I mounted, and there it was:

/dev/mmcblk0p1   3.8G   7.7M 3.6G 1% /media/4GSD

Right now it's an ext2 drive, but I'd like to make it jffs2 instead.
How do I create a jffs2 filesystem?  the documentation is really
confusing and the mkfs.jffs2 wants to make a tree from existing files.

owen

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