On Sat, Jul 18, 2009 at 04:21:56PM +0200, Andi Kleen wrote:

quoted

We don't have to rewrite fsck; most of the framework for supporting an
run-length-conding for compressed bitmaps is already in patches that
add > 32-bit block numbers to e2fsprogs; we've just been more focused
on getting 64-bit block numbers support merged than implementing
compressed bitmaps, but it's only one file that would need to be
added, and we might be able to steal the compressed bitmap support
from xfsprogs --- which does this already.

There are regular reports of xfs_repair failing on 32bit,
even on volumes far smaller than 16TB.

We have a set of patches pending to reduce memory use in xfs_repair
dramaticly, replacing bitmaps for tracking used blocks with extent
structures stored in btrees.