Re: [Cerowrt-devel] Is there a particular reason cerowrt isn't using UBIFS?

[David Lang <david@lang.hm>]

On Sat, 30 Aug 2014, Theodore Ts'o wrote:

>> A thing that irks me in the age of 4G flash becoming fairly common is the
>> general lack of compression aside from an option to btrfs. Debian barely
>> fits into 2 gb
>
> It depends on what you have installed, of course.  I have a debian
> test image which gets used for ext4 testing which is 189 megabytes
> uncompressed, and 57 megabytes using qcow2 compression (it gets run
> using qemu/kvm)[1].  It's a basic debootstrap image plus a handful of
> packages[2] plus xfstests (which is 22 megabytes uncompressed).
>
> [1] ftp://ftp.kernel.org/pub/linux/kernel/people/tytso/kvm-xfstests/
> [2] https://git.kernel.org/cgit/fs/ext2/xfstests-bld.git/tree/kvm-xfstests/test-appliance/packages
>
> This is still much larger than 7 megabytes in the Cerowrt's root
> image, granted, but it is possible to make a relatively svelte
> debian-based image.
>
>
> I've considered implementing MacOS X style compression (immutable
> files, compression which happens in userspace, with decompression in
> the kernel.)  The main reason why I haven't is that for most use
> cases, space hasn't really been that much of an issue, or most of the
> files are already compressed (i.e., Java or Dalvik classpath files
> which are already zip compressed).  It wouldn't be _that_ hard to do,
> but it's just not that high up on most people's priority lists.

One other place this sort of thing is likely to be useful is for Raspberry Pi 
and other small (embedded by some defintions) systems that use SD cards for 
their OS system. The I/O to the storage is so slow that the saved I/O time is 
likely to more than cover the cost of the decompression.

Raspberry Pi systems have had to move to 4G cards as their base because it's 
just not possible to have the standard install do more than boot on a 2G card.

David Lang