I wish this wasn't a video. When someone gives a talk, rather than just posting the video, won't someone at least post the slides? Or better yet, a transcript?
I'm having a really hard time refraining from writing a really snarky "Switch to MySQL" type response, not because I think that MySQL outperforms PostgreSQL, but because there is always somebody on every MySQL article discussion who does this. Ok, that's off my chest, sorry to rant.
I enjoyed this video, even though I'm not a PostgreSQL guy, as it has a lot of good generic info. The advice about XFS and noatime was right on the money, although I don't think he strongly stated enough why you don't want to run EBS volumes over software RAID-0. In my experience this is a really bad idea, because just one of those EBS volumes getting picking up a laggy await (happens pretty frequently with volumes I've seen in the wild) will drag down the performance of the entire array. Also I'm told that the old "RAID-5 is always bad" notion is considerably more nuanced nowadays, and that many of the earlier OLTP write performance problems with RAID-5 have been largely mitigated with modern RAID controllers.
" Also I'm told that the old "RAID-5 is always bad" notion is considerably more nuanced nowadays, and that many of the earlier OLTP write performance problems with RAID-5 have been largely mitigated with modern RAID controllers."
Not to be snarky, but do you have a source for that? RAID5 has a pretty big intrinsic write penalty.
"I'm having a really hard time refraining from writing a really snarky "Switch to MySQL" type response, not because I think that MySQL outperforms PostgreSQL, but because there is always somebody on every MySQL article discussion who does this. Ok, that's off my chest, sorry to rant."
I can think of good reasons to switch from mysql to postgres though, and I've a hard time coming up with reasons to switch from postgres to mysql (which is something else all together than choosing mysql over postgres in the first place - although even there, for serious deployments, the only real reasons I can see are in the "it's what we know" department).
Long time Postgres user so I may be a little biased ;-), but still.
This gave me the idea to try http://pgfouine.projects.postgresql.org he mentioned on my logs, and I'm already finding a bunch of stuff to fix after a quick run.
[+] [-] emmett|14 years ago|reply
[+] [-] simonw|14 years ago|reply
[+] [-] apu|14 years ago|reply
[+] [-] alnayyir|14 years ago|reply
Secrets of Postgres Performance
Measure Everything Before and After
Do not do Dumb Things
Cache Everything
Watch your query counts
Tuning Parameters
shared_buffers: set to 25% of available ram, move up/down 5% to find sweet spot
effective_cache_size: planning hint that tells PG how much RAM it can expect for OS disk cache
work_mem: per process amount of ORDER BY space
Other Parameters
wal_buffers: Set to 16MB and forget it
checkpoint_segments: Increase to at least 10
maintenance_work_mem: 50MB for every GB of RAM
synchronous_commit: turn off with data loss risks
Disks. Lots of disks.
Not all disks are created equal. Faster disks make a huge difference.
Configuration of disks matters a lot. RAID-5 is bad. RAID-1+0 is good.
Separate out the WAL onto its own disk. Can 4x write performance.
Worry about CPU after your disk/RAID/filesystem configurations are more or less optimal.
Use pgbouncer to pool connections
Tablespaces
Consider putting archive or legacy data onto slower drives/volumes
Separate your data and indices onto different volumes if possible
This applies even on SANs
Best of both worlds with Rackspace and Cloud Connect
EBS volumes and Software RAID is best but scary on AWS.
Choice of filesystem matters. No journaled filesystems for your WAL, it is a journal.
Use XFS for maximum performance.
USE noatime!
Avoid queries in loops.
Count() is slow
[+] [-] johnpaulett|14 years ago|reply
[+] [-] spudlyo|14 years ago|reply
I enjoyed this video, even though I'm not a PostgreSQL guy, as it has a lot of good generic info. The advice about XFS and noatime was right on the money, although I don't think he strongly stated enough why you don't want to run EBS volumes over software RAID-0. In my experience this is a really bad idea, because just one of those EBS volumes getting picking up a laggy await (happens pretty frequently with volumes I've seen in the wild) will drag down the performance of the entire array. Also I'm told that the old "RAID-5 is always bad" notion is considerably more nuanced nowadays, and that many of the earlier OLTP write performance problems with RAID-5 have been largely mitigated with modern RAID controllers.
[+] [-] jpitz|14 years ago|reply
[+] [-] jvdongen|14 years ago|reply
I can think of good reasons to switch from mysql to postgres though, and I've a hard time coming up with reasons to switch from postgres to mysql (which is something else all together than choosing mysql over postgres in the first place - although even there, for serious deployments, the only real reasons I can see are in the "it's what we know" department).
Long time Postgres user so I may be a little biased ;-), but still.
[+] [-] lflux|14 years ago|reply
[+] [-] toisanji|14 years ago|reply
[+] [-] alnayyir|14 years ago|reply