Mailinglist Archive: opensuse-factory (592 mails)

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Re: [opensuse-factory] Ditching ReiserFS?
  • From: Jeff Mahoney <jeffm@xxxxxxxx>
  • Date: Wed, 04 Oct 2006 11:48:27 -0400
  • Message-id: <4523D7CB.9050004@xxxxxxxx>
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Tobias Burnus wrote:
> Hi,
>
> Joop Boonen wrote:
>> Here are some links about OCFS2 (Sounds very good):
>> http://oss.oracle.com/projects/ocfs2/
>> http://en.wikipedia.org/wiki/OCFS2
>
> If I didn't search wrongly, neither quota nor ACLs are supported, yet.
> Otherwise, it indeed looks promissing.

There are a number of features that OCFS2 is missing, but they are being
gradually added. The OCFS2 guys (at Oracle, and some of us at SUSE) are
working on adding a lot of them. Sparse B-Trees are currently the big
holdup item, and once they're added, we get extended attributes (and
ACLs, by extension), sparse files, and hashed directories pretty soon
afterwards.

> PS: My favourite filesystem remains AdvFS of Tru64 Unix; it has a LVM
> build in. The filesystem can span several hard disks; you then create
> filesets on them. Each fileset can now occupy the whole free space (or
> up to a set quota limit). That way, one can have several separate file
> systems (actually file sets) without the need to specify the size. And
> it is a cluster filesystem as well.
> http://h30097.www3.hp.com/unix/advfs.html
> Unfortunally, it is not available for Linux.

Before my life as a Linux kernel hacker began, I was a system admin
running Tru64 systems. AdvFS had a lot of really interesting features,
but it was also quite fragile. I don't know how many times we ended up
needing to break out the salvage tool, which was essentially the same
thing as a reiserfsck --rebuild-tree -S, where it searches the disk
looking for *anything* that looks like it could be part of the file system.

I'm not convinced that having incorporating volume management into the
file system is a good idea. It worked well on Tru64 where there was only
two file systems of very different pedigree. On Linux, we have so many
choices of file systems that are all very good, and so there wouldn't be
a whole lot of advantage in integrating volume management into the file
system. We'd end up with a lot of duplicated (and potentially buggy)
code. With LVM2/dm/etc, we allow *any* file system that has the
capability to grow and/or shrink to take advantage of it.

File sets and file domains were an interesting concept, but I don't
think it would be too difficult to extend existing file systems to
behave similarly. The file system-global superblock could remain mostly
the same with the root directory containing entries on where to find the
sub-file system's superblock. The thing is, I just don't think it's a
feature a lot of people are looking for.

- -Jeff

- --
Jeff Mahoney
SUSE Labs
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