Comment # 9 on bug 950999 from Takashi Iwai

(In reply to Bernhard Wiedemann from comment #8)
> The download itself only contains an ISO9660 filesystem,
> but for some reason kiwi creates a btrfs on the remaining space
> file says it is
> > BTRFS Filesystem (label "hybrid", sectorsize 4096, nodesize 4096, leafsize 4096)
> 
> and probably overlays it as persistent storage
> instead of the tmpfs used when booting it as CDROM.

Yes, it's kiwi hybrid image, and what for live image.  You can save the data
there.  In the past, it was ext3/4, but it seems that btrfs is taken as the
default fs there, too.

> And that is where the btrfs/kernel invalid pointer dereference happens
> and brings the whole boot process to a standstill.

Right, this doesn't look good.  Do you still see this with the latest image?

I wonder whether we can test it on KVM somehow...

> (In reply to David Sterba from comment #7)
> > (In reply to Dr. Werner Fink from comment #6)
> > > BtrFS on a USB flash drive, ouch.
> > 
> > Why?
> 
> I think, it is not good because systemd-journal
> (same as old syslogd)
> does synchronous writes to the filesystem for each new entry,
> which causes a large write-amplification factor
> combined with the fact that most USB flash drives
> have very poor wear leveling algorithms
> which means that you can physically destroy the flash hardware
> within a few days of operating this way.

Well, btrfs isn't worse than others in this regard, even better.
But it's quite off topic, so let's stop here.  Only if there is a very solid
reason we shouldn't use btrfs for USB flash, it's worth to discuss.  But then
better in other place than Bugzilla.