On Tue, Oct 11, 2005 at 08:07:49PM +0100, ed wrote:
> On Tue, 11 Oct 2005 21:55:30 +1000
> "Rod.. Whitworth" <[EMAIL PROTECTED]> wrote:
>
> > RAID 1 (or any RAID really) is NOT a backup. It is a high availability
> > system.
> > High availability does NOT mean never unavailable.
>
> Hello again Rod,
>
> I've been looking at ways to make a redundant and load balanced SAN. As
> you put it, it's not high reliability, once you get a problem with RAID,
> or the box that it's attached to, you can consider the data 'unknown'.
>
> The best solution that I have seen is, although a bit of overkill, AFS
> (Andrew File System). It's kerberos based authentication on a token
> basis. Although I have not implemented it I see that it falls short
> because the tokens (if used) expire after 10 hours, which might require
> a cron job (if that fails does hell break loose?).
>
> Because it is limited to a single read/write node per volume, I see that
> a volume would be required for every directory that might take more than
> a few minutes to replicate to the read only nodes to avoid hammering the
> read/write node.
>
> All the other network distributed file systems seem under developed or
> unstable.
>
> FWIW there is something called DRBD which is considered the closest
> thing to RAID-0 over a network, it can fail sometimes with flaky results
> in testing. I have found it to be troublesom when problems occur during
> sync.
>
> Do you or anyone else know of anything that works better?
DRBD is RAID-1, actually (with n-way replication under development last
time I checked). I assume that was just a typo. ;-)
I can't say much more. Testing showed that running DRBD is possible and
replication does occur, under fairly non-loaded 'lab' conditions and
only testing failover in case of manually failing drives. However, I
ultimately decided not to pursue DRBD further.
I haven't looked at AFS too much, but seem to recall not looking into it
further after realizing the Kerberos auth issue you mentioned.
Joachim
