[Fedora-spins] The magic 4GiB squashfs filesize limit

[Jeroen van Meeuwen]

Bruno Wolff III wrote:
> On Wed, Jan 21, 2009 at 12:12:09 +0100,
>   Jeroen van Meeuwen <kanarip at kanarip.com> wrote:
>> Note that it really is the .iso file size we're talking about, and we 
>> really don't care about the >4GB squashfs image; it just so happens that 
>> if the contents of a .iso go >4GB, the .iso will go >4GB ;-)
> 
> I think this should have said if the squashfs image is over 4 GiB, then
> the iso will definitely be over 4 GiB.
> 

Yes, it should have said exactly that ;-)

>> This particular issue is raised by the Games Spin, which I consider one 
>> of the first downloads for a Windows user who may or may not be using 
>> vfat still. Lots of (Windows) people want to see what Games are 
>> available on Linux, right? A relatively greater portion of these Windows 
>> users (then say, Linux users) may still be using vfat, and that's what 
>> I'm concerned with.
> 
> Are there people that have a feel of what fraction of Windows users are using
> vfat for their C: drive?
> 
>> I wanted to vote on this during our last meeting. Either we block >4GB 
>> spins, or we allow them. So, the vote becomes: Do we allow .iso files 
>> over 4GB?
> 
> I believe that this was just going to apply to published iso's. My
> understanding is that it would be possible to pubished kickstart files
> that will require more space.
> 

Yes, the question is what the Fedora Project wants to release officially.

> With the change to livecd-tools now in rawhide, it will be possible for
> the squashfs file system to be over 4 GiB (by using udf instead of iso9660
> for the iso image). Most common DVD burning formats allow at least 4.7GB to
> be put a the DVD. This would allow about another 300MB to be added to an iso
> image (over the current limit) and still have it fit on a DVD.
> 
> For the games spin in particular exceeding the 4 GiB limit has benefits.
> I need to either cut a single large game that probably is a good example of
> what can be done on Fedora, several smaller games, or a good chunk of
> the desktop add ons over the base image.
> 
> Its hard for me to judge the trade off as I don't know how common vfat is
> for Windows users system drives. And the subset of users prone to trying
> Fedora iso's may not be representative of all Windows users.
> 
> USB flash drives are typically formated with vfat, but I don't think people
> are likely to download directly to a USB drive and if they want a portal
> way to move around a DVD image, the expected way to do that is on a DVD.

LiveUSB however is going to have the squashfs on the USB stick, probably
on vfat. I think this is an additional consideration we should make
regarding a general guideline of <= 4GB spins or > 4GB spins.

Kind regards,

Jeroen van Meeuwen
-kanarip