Hi Udo,
Multiple Magma Servers on one physical server: As Squeak/Pharo is not SMP-capable I was thinking of running one server image per physical CPU core on the DB Server. One of those images would host the primary while all other images would host read-only secondaries. As the requests are primarily read-only this should give (in theory) a more or less linear increase (with cores) in read performance ... or did I miss something?
No, your understanding is correct.
You may also consider, that if the application truly is strictly read-only (in terms of clients), then you can open multiple images on one single copy of the database, each with a _local_ connection. To do that, the best practice is to make a #fullBackup of the repository and host that copy read-only.
However, if you need updates then the HA approach is the right way to do it.
Local secondary server on Web frontend server: Given that the intended webserver machines are quad core I was thinking of running three seaside images + one secondary magma image on them. The idea is that a local read-only replica should be much faster to query than over the network. However I'm not even sure if it is possible for a MagmaClient to configure preferred servers. My current thinking is start a remote MagmaSession against the locally running (secondary) Magma server image. My understanding is that all read requests are handled by this server then - only write requests will be sent to the primary.
Yep, that's how it works. Please see the comment in MagmaNode>>#anySecondaryLocation for more information about how secondary locations can be chosen. :)
Am I making things much too complicated?
No, but I would ask whether you've looked at the #statistics of your MagmaSession clients and determined that they are, in fact, waiting on the server? A server usually can handle several active MagmaSession clients, and maybe that's what each of your web-servers is doing; employing enough MagmaSession clients to saturate the server. If that is the case, then HA configuration will help.
- Chris