patch draft for extended attributes on linux

[Martin Pool]

On 24 Jun 2003, jw schultz <jw at pegasys.ws> wrote:
> That lack of an mtime for xattr could well cause
> difficulties for backup systems as well.  Perhaps a note to
> the filesystems people is in order.  The problem is that you
> can't use mtime for these.  It really needs its own
> timestamp, perhaps as a mandatory system attribute.

Yes, I think so.  If that still makese sense when I'm finished on this
I will send mail.

Perhaps it would fit well into the reiserfs 'tree of small things'
model of the world.

> I don't much care for sending the xattrs as part of the file list.
> Even the 4KB ext[23] _currently_ limit it to is huge.

I'm not sure what is typical here.  The situation I'm working on is
replicating a Samba share which is storing ACLs and EAs in XFS EAs.
Most of them will be pretty small, and most files won't have them.  

For a small tree with a short XA on each file and no other changes,
it's like this:

    [data]$ ~/work/rsync/xa/rsync -aPzv distcc-2.7.1/ dest --xattr
    building file list ...
    161 files to consider
    wrote 12365 bytes  read 20 bytes  24770.00 bytes/sec
    total size is 1115540  speedup is 90.07
    [data]$ ~/work/rsync/xa/rsync -aPzv distcc-2.7.1/ dest
    building file list ...
    161 files to consider
    wrote 3027 bytes  read 20 bytes  6094.00 bytes/sec
    total size is 1115540  speedup is 366.11

I think it's tolerable.

-- 
Martin