CODA filesystem

[Shawn T. Rutledge]

So I see the same old disclaimers are still on the web site about it
not being stable enough for prime time, but it sure has been a long time...
I remember JLF saying he was using it a while back.  Anybody else?

I have had too many problems which sometimes resulted in /home being
offline.  Right now it's on the primary Linux partition on my main 
workstation (the one where I went through all the install hassles last
weekend) which is convenient for speed but very bad for reliability.
I export it via NFS to my other systems.  Usually I run mutt on top of
screen on my gateway machine to read email from either work or home;
and mutt cannot write to folders in my home directory because of NFS
locking problems.  The mutt developers seem to be really strict about
doing what is correct rather than what works or is convenient... so this
bug waits for a fix to NFS, which has been broken so long I don't expect
much (seem to remember there being fundamental discord over how to do
locking, and whether it even should work for NFS the same as it works for
local disk).  And, the web server depends on /home too; if it's not
mounted, most of my web pages aren't available.  So all of this makes 
me want to try Coda, for the following reasons - 

1.) network filesystem without NFS's limitations, if I'm lucky
2.) I could use 2 or 3 servers, replicate and have enough redundancy
    to alleviate my fears about not doing backups often enough (and
    these days, a tarball of /home doesn't fit on one CDR anymore
    like it used to)
3.) the local cache should make it faster; and/or maybe it will be
    faster for other reasons too - NFS is not known for speed
4.) maybe I could use ReiserFS, and avoid the NFS bugs which occur when
    using ReiserFS and NFS together

The ideal distributed filesystem would be a peer-to-peer aggregating one
which also insures "n" levels of redundancy (configurable); it would
aggregate free disk space on all the machines on the network.  But such
a thing doesn't exist in a way which can actually be mounted and used as
a regular filesystem, AFAIK.... so in the mean time there's Coda.

My best candidate for a file server at this point is probably Tachyon,
which has a 17 gig drive that is only getting used for MP3's and backups
so far.  I could put the MP3's in my home directory and use the entire
disk just for /home.  But I think Coda requires servers to have the same
size disks if you're doing replication and failover, right?  Because all
the files have to exist on both drives?  AFAIK it doesn't do aggregation.
So maybe I should get a pair of nice new 40 gig drives instead - they 
sure are cheap enough.  I would put one in Tachyon, the dual Celeron 
box, and another in a slower box (I have an extra P75 laying around, and
an extra rack case with nothing in it; this box could also have about 
6 CDROMs mounted in it, which is something else I've been wanting to do.)
So my question is then, which server should be the SCM, the faster less
reliable one (which could conceivably be used to do more stuff besides 
being an NFS server, and is likely to get its kernel upgraded from time
to time) or the slow one that I get working once, get it stable and then
not expect it to do anything else?  Will Coda automatically figure out
that one box is faster and try to get files from that one most of the time?
Or will it prefer to get files from the SCM if possible and only if it's 
not available, fail-over to the replicant?  Will the speed even matter
or will it be quite fast because of the client-side cache?  

If speed doesn't matter a lot, I could even put a tertiary even-more-
reliable machine (a 486 maybe) in a different room as yet another
failover machine.  It would have its own little UPS, ext2 filesystem
(just in case Reiser develops problems) and absolutely no other tasks 
besides acting as a backup.

Why is there a limit of 300 megs for client-side cache?  (This wasn't
explained on the web site, they just said not to do it.)

Given that Coda puts all the files in one giant directory, is ReiserFS
vastly superior, because as I understand it's much more efficient than
EXT2 for large directories?  Are Coda and ReiserFS known to get along?  
Which version of Reiser should I run, the latest, or the latest even-
numbered one?

Do file conflicts arise often enough in practice to be a pest?

-- 
  _______                   Shawn T. Rutledge / KB7PWD  ecloud@bigfoot.com
 (_  | |_)          http://www.bigfoot.com/~ecloud  kb7pwd@kb7pwd.ampr.org
 __) | | \________________________________________________________________