On Fri, Mar 23, 2012 at 11:18 PM, Bret Stern <bret_stern@xxxxxxxxxxxxxxxxxxxxx> wrote: > VoltDB maybe > ----- Original Message ----- VoltDB has a completely different focus than PostgreSQL really. PostgreSQL is a general purpose database that can achieve some very impressive numbers using super fast hardware, while still being a general purpose db that can do more than just shove through thousands of transactions a second. For instance, I've tested machines with spinning drives that could sustain, for weeks, 5 to 7k tps. Autovacuum suitably tuned to be fast enough to keep up (i.e. no sleep time, greatly increased cost ilmit, lots of checkpoint segments, and very aggressive bgwriter settings as well. I can imagine doubling that with a rack of SSDs behind it. And all on a single machine, that can be running PITR or streaming replication at the same time. VoltDB accomplishes this kind of throughput by running in memory, doing a kind of auto-sharded, RAIDed database setup for redundancy. I imagine a farm of little 1U 8 or 16 core machines running multiple instances of VoltDB (individual instances are single threaded) could just stomp pg right into the ground as a transactional engine. Because now you're scaling horizontally No matter how fast the hardware underlying it gets, pg will have a limit by the laws of physics on an individual machine that VoltDB simply works around by having dozens or hundreds of individual boxes doing the same job, albeit in a very specilalized manner. I've not played with VoltDB and I don't know how stable and reliable it is yet, but it was built by Michael Stonebraker, so I'd expect it to at least hold the promise of stable operation as it matures, if not being stable and reliable now. But the % of db systems that need that level of performance are pretty limited, and generally designed to have a large chunk of the world's population working on them at the same time. For a system that's more typical, i.e. 95% or more read, you can throw memcache in front of even a pretty mediocre box and have it keep up just fine for hundreds or even thousands of writes per second and hundreds of thousands of reads to the cache layer per second. There are real world problems with redundancy and reliability to work out with VoltDB that are quite different from Postgresql, since you need real synchronous replication from two geographically separated data centers, because if something horrible happens in one, (it gets hit by a meteor, or some junior electrician drops a piece of wire into a power conditioner, one whole segment of your db fabric could go dark. And if it's not synchronous, then the replication is useless for a true transactional banking style system. Keep in mind a pg server simply losing power is usually safe from data loss, and a nearby machine with syncrhonous replication is likely to provide a high enough level of redundancy for most transactional systems. Since VoltDB is in memory, you HAVE to have a live backup running somewhere remote, or a simple power loss kills all your data / latest transactions. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
