On Wed, Jul 15, 2009 at 04:14, Martin Langhoff<martin.langh...@gmail.com> wrote: > On Wed, Jul 15, 2009 at 8:35 AM, Greg Smith<gregsmit...@gmail.com> wrote: >> As I got there I noticed a kid had unplugged their USB before full >> shut down and they were frantically trying to plug it back in while >> errors scrolled on the screen. Still not sure if they lost data (will >> check tomorrow on kid who made the same mistake last week). Is there >> anything we can do to ensure that all data is written/saved ASAP on >> clicking Shut down from the menu? > > This is a very valid concern, and very tricky. I've seen lots of > problems with LiveUSB sticks and unclean shutdown. > > The short of it is that the scheme behind "LiveUSB", specifically the > "persistent storage" is very brittle, to the point that it can hose > the entire disk badly. The USB stick will only be usable again after > re-formatting and re-installing the SoaS software (losing user data, > etc). > > It is a bad combination of > > - Using "rw" overlay mountpoints that only sync every 5s. If the > overlay partition is corrupted, it will prevent the SoaS from booting. > > - Writing on a FAT partition which is notoriously fragile... and > mounted async. Mounting it sync slows things tremendously and wears > the USB stick out much faster. > > IIRC, recent kernels have a mount flag for vfat (and maybe other FSs?) > that makes the kernel more eager to flush things to disk, so you can > keep the mountpoint async but reduce the 5s window significantly. > > Unfortunately, I can't find it now. It was well reported on LWN and > kernelnewbies a few months ago.
I agree with the conclusion that Linux support for live usb sticks still has a long way to go. See https://bugzilla.redhat.com/show_bug.cgi?id=465725 for more details about the overlay issue, though note that in Fedora the whole stick is not thrashed, you can discard any changed you did to / by passing the kernel the option reset_overlay. If deployers of SoaS keep in mind this limitation and users mostly write inside /home, this limitation is much less important. This really has very little to do with Sugar itself, like hardware support. I think we need to find the resources to make the needed work in the kernel and in the distro level before we can do anything in SoaS itself. Regards, Tomeu > cheers, > > > > m > -- > martin.langh...@gmail.com > mar...@laptop.org -- School Server Architect > - ask interesting questions > - don't get distracted with shiny stuff - working code first > - http://wiki.laptop.org/go/User:Martinlanghoff > _______________________________________________ > Sugar-devel mailing list > Sugar-devel@lists.sugarlabs.org > http://lists.sugarlabs.org/listinfo/sugar-devel > _______________________________________________ Sugar-devel mailing list Sugar-devel@lists.sugarlabs.org http://lists.sugarlabs.org/listinfo/sugar-devel