>We aren't sure why, but when we tried to delete a lot of data (~200GB from each machine which each contain several TB of data), our databases become unresponsive for an hour.

There used to be an issue where users hitting their quota couldn't delete files since for some reason deleting a file meant creating a file somehow. The trick was to find some reasonably large file and `echo 1 > large_file` which truncates the file and frees up enough space that you can begin removing files. Maybe this kind of trick could help you guys.

That said, it's inadvisable to run a database on a btree file system like ZFS or btrfs if you're keeping an eye on the write performance. cf Postgres 9.0 High Performance by Gregory Smith (https://www.amazon.com/PostgreSQL-High-Performance-Gregory-S...)

and

https://blog.pgaddict.com/posts/postgresql-performance-on-ex...

Yes, totally different thing. :-) A great book on query plan stuff is here:

http://www.amazon.com/PostgreSQL-High-Performance-Gregory-Sm...

You might be interested in this

http://www.amazon.com/PostgreSQL-High-Performance-Gregory-Sm...

If high-performance PostgreSQL is critical to your job, here are some resources:

http://wiki.postgresql.org/wiki/Slow_Query_Questions

Query analysis tool http://explain.depesz.com

The mailing list http://www.postgresql.org/list/pgsql-performance/

Greg Smith's book http://www.amazon.com/PostgreSQL-High-Performance-Gregory-Sm...

#postgresql on freenode.net

There is this book: http://www.amazon.com/PostgreSQL-High-Performance-Gregory-Sm...

I haven't had a chance to finish it. But it does look like the author knows what he's talking about.

They ink to PostgreSQL 9.0 High Performance (http://www.amazon.com/gp/product/184951030X/), which I agree is a great book if you're a sysadmin supporting PostgreSQL.

Greg Smith's PostgreSQL 9.0 High Performance [1] Cary Milsap's Optimizing Oracle Performance [2], and - a pale third, Davidson and Ford's Performance Tuning with SQL Server Dynamic Management Views [3]

The first 2 are bottom-up, structured approaches to benchmarking low-level system performance with an emphasis on *nix, and building up to database performance characterization and investigation. Despite their names, both have a lot of great general, non-product-specific use.

The third I include because it is the only MSSQL-specific book I have on the subject, and it sounds like you're in Windows Land. It has some real gems, but little coverage of the OS or methodology. I cannot over-emphasize how important that methodology is.

Make sure you learn how to use the Resource Monitor, and SQL Profiler.

If you want to chat about it more, I'm justinpitts at google's mail.

[1] http://www.amazon.com/PostgreSQL-High-Performance-Gregory-Sm... [2] http://www.amazon.com/Optimizing-Oracle-Performance-Cary-Mil... [3] http://www.amazon.com/Performance-Tuning-Server-Dynamic-Mana...