High availability ... again

[Kevin Baker]

David,

This is exactly what I had in mind. Could you maybe give a
quick overview of how you have the replication and
failover setup; specifically "application level
replication vs block"

While the idea of a standby server that uses block level
replication seems very great, if possible I'd like to have
the reliability while still being able to use both
machines.

Is it something like this:
- Server A
  - active accounts 1-100
  - replicate accounts 101-200 from Server B
- Server B
  - active accounts 101-200
  - replicate accounts 1-100 from Server A

If B goes down, A takes over the accounts it had
replicated from B.


Thanks,






> On Tue, 22 Jun 2004, Etienne Goyer wrote:
>
>> Does somebody on the list use this solution or a similar
>> one and could
>> comment and the practicality of it ?  Perhap M. Carter
>> (if you read the
>> list) could give us a status update for his particuliar
>> project ?
>
> There's really not a whole lot to say.
>
> We've been using the code on our main 32k user mail system
> since about
> this time last year for data migration, fast incremental
> backup to a tape
> spooling system, and rolling replication for live updates.
> We also used
> the replication system to migrate from a UW based system
> to Cyrus.
>
> We have 16 small Linux servers running as 8 pairs. All the
> systems are
> live Cyrus servers, half the accounts on each system are
> replica versions.
>
> One of the 16 had a hardware fault a couple of weeks back
> and noone has
> moaned at me after we switched to the replica which is
> always a good sign.
>
> From my perspective the advantage of application level
> replication over
> block level replication like DRDB is flexibility.
> Read/write access to
> both master and replica systems can be useful: we maintain
> databases
> of MD5 checksums for all the messages and cache entries on
> each server.
> Its also rather cute to run PINE against both master and
> replica version
> of a given mailbox and watch the replica play follow my
> leader :).
>
> --
> David Carter                             Email:
> David.Carter at ucs.cam.ac.uk
> University Computing Service,            Phone: (01223)
> 334502
> New Museums Site, Pembroke Street,       Fax:   (01223)
> 334679
> Cambridge UK. CB2 3QH.
> ---
> Cyrus Home Page: http://asg.web.cmu.edu/cyrus
> Cyrus Wiki/FAQ: http://cyruswiki.andrew.cmu.edu
> List Archives/Info:
> http://asg.web.cmu.edu/cyrus/mailing-list.html
>

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