![]() ![]() ![]() Granting consent to receive the CYBERTEC Newsletter by electronic means is voluntary and can be withdrawn free of charge at any time.įurther information can be found in the privacy policy. Yes, I would like to receive information about new products, current offers and news about PostgreSQL via e-mail on a regular basis. Weitere Informationen finden Sie in der Datenschutzerklärung. Ich kann diese Zustimmung jederzeit widerrufen. Ja, ich möchte regelmäßig Informationen über neue Produkte, aktuelle Angebote und Neuigkeiten rund ums Thema PostgreSQL per E-Mail erhalten. when going for synchronous replication, the differences between “remote_apply” and the default “on” are when going for synchronous replication you will lose ca 1/4 of your performance.by turning off “synchronous_commit” you get a very significant TPS boost and it indeed can be used as a temporary performance crutch.“remote_apply” sync – 3055 TPS (-8% compared to “sync on”)įirst, as always – performance numbers rely on a lot of things, with synchronous replication especially a lot on network performance/distance, so your mileage will definitely vary, but I think we can still note a few things from here: ![]() “remote_write” sync – 3720 TPS (+12% compared to “sync on”) “on” sync – 3329 TPS (-22% compared to default “async on”) “off” async – 6211 TPS (+45% compared to default “async on”) “on” async – 4256 TPS (FYI – here 1 transaction means 3 updates, 1 insert, 1 select) On a pair of AWS EC2 i2.xlarge instances (good starting point for a busy application as its I/O optimized, 4 vCPU, 30.5 GB RAM, 800 GB SSD) I got the following numbers for a shortish 10 minute test period on a “pgbench” scale 100 size dataset (dataset fits in RAM) with 8 concurrent clients: The script can be found here so I will skip details for brevity and just present you the TPS (transactions per second) results. * off – Commit can be acknowledged to the calling client before the transaction is actually flushed to the transaction log, making it possible to lose some recent ( on (async) > remote_write (sync) > on|local (sync) > remote_apply (sync)īut what would the penalty in numbers be when using higher consistency levels? How much slower would the transactions get? Let’s do a set of quick tests again with our good old buddy pgbench!įor testing, I created a primary-replica setup on AWS and a script running through different parameter values, re-starting and re-initializing the test schema for every parameter. In synchronous streaming replication mode also the replica needs to do the same. * on – Transaction commit always waits until the data is really flushed to the transaction log (aka WAL or XLOG) making sure the transaction is really persisted. NB! Latter 3 values are effective only in synchronous streaming replication mode and fall back to “on” value when no replicas have been listed in the “synchronous_standby_names” parameter. Short descriptions of all of these in plain-text could be something like that of below. Options availableĪllowed values up to Postgres version 9.5 were – “on”, “remote_write”, “local” and “off” and now with 9.6 “remote_apply” will join the party. And in soon to be released PostgreSQL 9.6 another new option called “remote_apply” was added so I thought I’ll take it for a spin out of curiosity, while also trying to explain the other options in simple terms and to perform some testing in a streaming replication scenario, with and without synchronous replication. It’s one of the important-ish parameters with an above average amount of options, which could be a bit daunting for the casual DBA. If you’re not yet familiar with the Postgres “synchronous_commit” parameter you should definitely keep reading. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |