Re: [PATCH] Btrfs-progs: btrfs file system size should be bigger then 256m

[Tomasz Chmielewski <mangoo@wpkg.org>]

Kaspar Schleiser schrieb:
> Hey,
> 
> Tomasz Chmielewski wrote:
>>> This has been bothering me for some time. Why does btrfs need to have 
>>> a disk greater then 256M? I could see a much smaller limit, say 16M 
>>> but why so much? The file system itself does not need that much space 
>>> for its own use.
>>
>> In other words, 256M limit rather disqualifies btrfs as a filesystem 
>> i.e. for /boot, doesn't it?
> When 1G is just 10c?

Maybe when talking about traditional HDDs.
Anything flash-based is still $2-$5 per 1G.

I have some SAN devices booting off 512MB or 1G builtin flash. Having 
256M for /boot there would not leave much more space for the operating 
system.

Why separate /boot? It's still needed for encrypted rootfs or more fancy 
partitioning (like / on LVM, at least until GRUB2 is stable and is 
shipped by major distros).


Seriously, what are the technical reasons that btrfs needs so much space 
for a minimal filesystem?

Just 2 MB is enough for mkfs.ext4 to create a valid filesystem.


Also, the patch seems to be incomplete - i.e. what will happen if we try 
to btrfs-convert a 50MB ext3 filesystem into btrfs?


-- 
Tomasz Chmielewski
http://wpkg.org