Forum OpenACS Q&A: Re: OpenACS clusters
The AOLserver clustering support in OpenACS seems like a useful addition for flexibility, but I'm not sure how relevent it really is for a current site with any sort of reasonable hardware budget.
Supermicro now sells 4-socket Opteron servers at no price premium over 1 and 2 socket boxes; they're priced essentially linearly with the number of sockets. That means you can easily buy an either 1u or 2u box with 4 sockets, 48 cores, and 256 GB of RAM for $15k or so. (You can go up to 512 GB RAM on that same 4-socket motherboard, it just gets pricier.) How many OpenACS sites need more than 48 cores and 256 to 512 GB of RAM for their web servers? My guess is that's plenty even for big sites like WU-Wien. Spend a little more on disks and possibly a good hardware RAID controller, and you could also use that same 2u box for your RDBMS.
For more disk-intensive RDBMS loads, particularly analytics rather than the more OLTP-like loads typical of most OpenACS sites, I'd like to try some of Scalable Informatics' JackRabbit and/or DeltaV boxes. They seem to give massive streaming IO bandwith, and if one 48 disk box isn't enough, they also offer them configured as a storage clusters, optionally with a high-end Infiniband interconnect.
For the high-end storage cluster route, I'm not sure if any of the current cluster file systems are suitable for running an RDBMS, but if not, it'd probably work reasonably well to have your single RDBMS box use each of those 48-disk boxes as a giant "local" RAID-10 array. You'd want to make sure the PCI-E bus(es) on your RDBMS box can handle the bandwith, though. At some point that single RDBMS box will top out, and to get even more CPU and/or disk IO, you'd need to either look at more specialized (and pricey) giant SMP/ccNUMA boxes, or real shared-nothing clustered databases - Teradata or their newer cheaper competitors (some of which are PostgreSQL based).