[Libvir] Re: parted/LVM for ET [Storage manager initial requirements and thoughts

[Jim Meyering]

I'm reviving this old thread to give you all an update.

    http://thread.gmane.org/gmane.comp.emulators.libvirt/826

I've been working on parted for some time now,

    http://git.debian.org/?p=parted/parted.git;a=summary
    http://news.gmane.org/gmane.comp.gnu.parted.devel

and have just recently discovered a few problems with its ext2 file system
support.  I fixed one bug that I just stumbled upon, and another one or
two have proposed fixes that look good.  However, after investigating
those, I am convinced we need to dump libparted's ext2 FS support ASAP,
in favor of the e2fslibs (libext2fs) library that is used by e2fsprogs.
It appears to be very well maintained and robust, while the ext2/FS code
in libparted is obviously in bad shape.  For example, mkfs would fail
for many sizes, and resize would fail for even more, given an initial
partition size in certain ill-fated ranges.  So far, I haven't seen too
many file-system-corrupting bugs, but I think that's mainly luck.

In addition, there is the fact that Parted's partition-table (aka
what it calls "label") support is currently tied to a 512-byte sector
size for many label types.  BTW, do any of you know which are the
partition types that matter the most to us?  MSDOS and GPT seem like
the top priority ones, and I've fixed most parts of those two, but
have only lightly tested the GPT changes.  Also, with >512-byte sector
devices becoming more and more common (e.g., ipods, CDs, new-and-bigger
disks), I wonder how important it is to make Parted work for them, now.
Fixing Parted for the few most common partition types isn't a big deal,
but fixing all of them would require more time and testing resources than
I expect to have.  I plan to leave most of the others in their current,
works-only-for-512-byte-sectors state.

Also in line with limiting scope, I'm concentrating only on the few file
system types that are likely to be useful here: obviously, we care about
ext2 and ext3 (which Parted will get for free, with the e2fsprogs graft),
probably FAT32, too.  Does anyone think some other FS type deserves
attention right away?

Since my initial handful of patches in LVM/device-mapper land, I've done
little on that front, and I don't expect to resume work on it until some
time in July.

Jim