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A fourth option, for those in physical datacenters who do not need to run active/active, is of course to eschew network replication entirely in favor of a RAIDe
by colanderman 9y ago
A fourth option, for those in physical datacenters who do not need to run active/active, is of course to eschew network replication entirely in favor of a RAIDed JBOD shared between two or more servers. If you have the hardware, this is often the easiest to configure, and the most efficient.
EDIT: I should clarify that, like the other HA solutions in the article, of course you need to couple this with a backup solution, like periodic dumps to S3, such as the article suggests.
- colanderman 9y agoThose downvoting, care to give a technical reason why I am wrong?
- koolba 9y agoThe short answer is that RAID is not a backup solution.
- colanderman 9y agoI didn't say it was? Nor is replication. But thanks for the reply, I've edited to clarify that disk sharing is an alternative to the three HA solutions in the article, not the one backup solution (which in all examples is the mundane "copy to S3").
- rosser 9y agoThe Fine Article is, indeed, light on meaningful approaches "backup", despite its prominent presence in its title.
- colanderman 9y agoIt's also light on approaches to HA (hence my – apparentely misunderstood – addition to the list). Postgres's documentation itself is much more thorough: https://www.postgresql.org/docs/10/static/different-replication-solutions.html https://www.postgresql.org/docs/10/static/different-replicat... And gives a little more insight into backup options too: https://www.postgresql.org/docs/10/static/backup.html https://www.postgresql.org/docs/10/static/backup.html
- rosser 9y agoIt also doesn't manage failover. Shared storage is a totally viable approach. (I've worked as a PostgreSQL DBA for over a decade and have built multiple shared storage-based HA environments for multiple employers.) If you mis-manage failover, you will destroy your data. This makes proper backup even more important.
- colanderman 9y agoNor does Postgres replication manage failover. Either way you need a 3rd party tool. Yep, botched failovers are bad. Of course, a botched failover between replicated DBs is no walk in the park either. In many such cases you'll still want to pull backups anyway, if there's no clear way in your domain to merge two "authoritative" databases.
- rosser 9y ago> In many such cases you'll still want to pull backups anyway... In all cases where you care about your data, you must take backups. There is no substitute for that step. Additionally, you want to periodically restore your backups and test them for validity — ideally automatically. There's a saying in the ops world, borne of bitter experience: "Your backups are only as good as their last successful restore."
- grantwu 9y agoI read "pull backups" as "restore from backup" not "make backups".
- colanderman 9y agoWhat grantwu said. You misinterpreted me. Seems to be a theme today. I guess I should spell things out more clearly in the future.
- rosser 9y agoOk, my apologies. I've never heard that phrasing before, but now that you clarify, I understand it. Ambiguity in online discourse is an ongoing problem. Thanks for helping resolve this occurrence without acrimony.