11:24

Small PostgreSQL Installations and 9.0 Replication

28 October 2010

Yesterday, I commented on a post about how widespread uptake on 9.0 replication will be. I disagreed with the assessment that “users” (by which we mean small installations of PostgreSQL, defined however you care to) will not be interested in 9.0’s hot standby/streaming replication.

Ultimately, of course, we’ll find out. But I strongly feel that 9.0’s streaming replication will be a big deal for small PostgreSQL installations… indeed, I think it will be a much bigger deal for them than big ones.

First, I’ll happily exclude hobbyist and developer installs of PostgreSQL. I don’t back up my development PG databases more often than once a day, and I certainly don’t have any kind of replication set up for them (unless that’s what I’m developing). The important part, the code, lives in a DVCS, and if I had to reconstruct the db from scratch, no big deal… indeed, I do it all the time.

I’m talking about small installations of PG that are used to as authoritative records of business-critical information: Web site transactions, for example. The fact that, traditionally, these users of PG haven’t been all that into replication solutions has nothing to do with their actual need for replication; instead, it has to do with the solutions they had available.

• Small installations generally don’t have the time and expertise to search out third-party solutions, or the budget to pay an expert to do so. If it doesn’t come in the base RPM or tarball, they’re not interested in it.
• The third-party solutions that are available are all complex and fiddly to set up. I’m certainly not bashing Slony, for example; it’s a great tool. But it is not something that a casual DBA wants to take on.

So, they make do with pg_dumpall and hope for the best… and then call someone like us if that doesn’t work.

But it is fallacious to conclude that because they are not using replication right now, they have no use for it. Ask a corner liquor store if they could afford to have an entire day’s worth of electronic transactions just vanish; I’ll bet a bottle of something cheap that they carry that the answer would be, “Of course not.” It might not be worth a $15,000 consulting engagement to set it up, but it’s worth something, possibly quite a bit.

Indeed, this is one of the things that’s driving adoption of “cloud computing”: The (sometimes erroneous) idea that the cloud provider is managing disaster recovery and high availability for you, included in the cost of your monthly service charge.

tl;dr: PG 9.0’s streaming replication will be widely adopted by smaller installations that use PG to manage business-critical data, specifically because it makes it something a casual DBA can do, something we’ve not had before with PG.

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