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* Kjetil Torgrim Homme <kjetilho@???> [20040105 20:02]: wrote:
> On Mon, 2004-01-05 at 11:37, Odhiambo G. Washington wrote:
> > My New Year resolution is to establish a system that will support both
> > redundancy and high availability. This will only involve two boxes
> > running Exim on FreeBSD platform. The users will be in a MySQL db but I
> > also have file-based lookups.
>
> okay, but then the MySQL db becomes the single point of failure, and it
> is also hard to keep the files in absolute sync across Exim servers.
> the latter may not be a big problem, depending on your configuration,
> but you need to consider what happens when they're out of sync -- can
> e-mail messages loop?
My configuration is such that the servers simply do a lookup, they don't
write to the database. The DB is going to run on a single server, from
where all lookups will be done. It's also going to be replicated on
another server just for backup purposes only.
> we're using LDAP generated from a database as our backend for _all_
> configuration data. replicating an LDAP service is a well-known
> problem, and many organizations need that anyway for other services.
I am not intending to touch LDAP so soon ;) I have no clues about it
even as we speak.
> the other problem is the storage. you don't say if you want to do
> active-passive or active-active failover. with active-active you need a
> storage system which allows simultaneous delivery from more then one
> host.
This is where I am totally green. I will need a lot of help in making a
decision about storage since it's not anything I have used before. My
thinking was along the lines of "shared" storage. Beyond that is what
forms the true scope of my request to the list.
> in our old system, we used NFS for this (a NetApp), but this does not
> scale very well. in our new system, we're using 12 virtual Cyrus
> instances in HP ServiceGuard running on three physical servers, hooked
> up to a RAID system via Fibre Channel. each Cyrus instance has a LUN on
> the RAID containing all data associated with it. we use Perdition
> IMAP/POP proxy software in front of these (with active-active failover
> courtesy of LVS) to make them look like one server to our users. Cyrus
> Murder may be just as good or better. but this is likely much more
> hardware than you need.
If I am allowed to summarize my understanding of the above paragraph,
i'd simply say "greek" ;) However, it surely shows you really understood
what I am after. I am glad.
What kind of investment (budgetwise and in terms of new knowledge to
acquire) are we looking at here??
Besides the fact that I haven't seen any such hardware (well, I was
thinking also along the lines of NFS, and I have heard people talk about
NetApp on this list also, but never read about it before), I am looking
at something that is "simple but achieves the goal". I believe simple
here is not quite synonymous with "cheap", but we're not looking at
investing in "very expensive" hardware.
It seems like I have to google for a few terminologies here:
ServiceGuard
Cyrus Murder
LUN
Perdition
LVS
-Wash
http://www.netmeister.org/news/learn2quote.html
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