[Bug-gnupod] Gnupod documentation should include warning about mounting with "sync" option for flash-based iPods

[Jim Pivarski]

I bought an iPod shuffle and used Gnupod to fill it, never having seen an iPod working on Mac/PC and never having used a flash drive before.  The shuffle is a single-partition, VFAT-formatted flash dongle which connects directly to a computer's USB port, so I read but didn't apply the sections on firewire and VFAT formatting.  The one piece of information I used was the suggested /etc/fstab entry:
> /dev/sdb1       /mnt/ipod       vfat    defaults,users,noauto,sync,umask=000
I didn't know what "sync" means, but I assumed it was appropriate.  File transfers were very slow (maybe 10 minutes per megabyte), but I didn't know (or think) that this was a problem.  About a week later, my iPod failed completely (no partition table, and eventually, no device showed up in the USB chain).  Assuming it was faulty hardware from the factory, I replaced it at the store.

With my new iPod, I got curious about the slow file transfers because the speed seemed to be non-linear: the first few files transferred quickly and the rest were slow.  After some searching online, I found this:
> http://www.ussg.iu.edu/hypermail/linux/kernel/0505.1/1249.html
which says that (contrary to the documentation) VFAT 
does not ignore the "sync" option, and that Linux excessively re-writes the FAT tables when "sync" is applied.  I also learned that flash drives have limited lifetimes, measured in write cycles.  I removed the "sync" option and found that write access picked up dramatically; only unmounting is slow (evidence that the "sync" option is not being ignored).

I don't know how long my new iPod will last (I wrote to it with the "sync" option overnight), and I'll probably never be able to get a new one like it (my favorite model has been discontinued; I don't want a screen or a special adapter for USB), but that's my problem.  Please, please, please include the following warning in your documentation for future readers:
> If your iPod is a flash device (rather than a hard drive), do not mount with the "sync" option, as this will destroy your iPod.  When you mount, 
> do not include "-o sync" and in your /etc/fstab file, do not include "sync" in the options list. 
>  Just be careful to unmount your iPod before disconnecting it from the USB or firewire port, because not all of the data is transferred until you explicitly "unmount."

Thank you.
-- Jim