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If you’ve been tuning your MySQL database and have wondered what effect the innodb_flush_method settings have on write performance, then this information might help. I’ve recently been doing a lot of baseline load tests to show performance differences between localdisk and the new SAN we’re deploying. Since we run InnoDB for everything in production, and writes are very heavy, I decided to run comparison tests between two identical servers to find the best setting for innodb_flush_method. We have the following specs for the hardware:
There are about a gazillion FAQs and HOWTOs out there that talk about XFS configuration, RAID IO alignment, and mount point options. I wanted to try to put some of that information together in a condensed and simplified format that will work for the majority of use cases. This is not meant to cover every single tuning option, but rather to cover the important bases in a simple and easy to understand way.
Let’s say you have a server with standard hardware RAID setup running conventional HDDs.RAID setup
For the sake of simplicity you create one single RAID logical volume that covers all your available drives. This is the easiest setup to configure and maintain and is the best choice for operability in the majority of normal configurations. Are there ways to squeeze more performance out of a server by dividing the logical volumes: perhaps,[Read more...]
Before I start a story about the data recovery case I worked on yesterday, here's a quick tip - having a database backup does not mean you can restore from it. Always verify your backup can be used to restore the database! If not automatically, do this manually, at least once a month. No, seriously - in most of the recovery cases I worked on, customers did have some sort of backup, but it just wasn't working, complete and what not. Someone set it up and never bothered to check if it still works after a while.
Anyway, this post is not really about the backups but rather about few interesting things I learned during last recovery case.
First, some facts about the system and how data was lost:
This miniconf aims to cover many of the current methods of data storage and retrieval and attempt to bring order to the universe. We’re aiming to cover what various systems do, what the latest developments are and what you should use for various applications.
We aim for talks from developers of and developers using the software in question.
Aiming for some combination of: PostgreSQL, Drizzle, MySQL, XFS, ext, Swift (open source cloud storage, part of OpenStack), memcached, TokyoCabinet, TDB/CTDB, CouchDB, MongoDB, Cassandra, HBase….. and more!
There seems to be two options on Win32 for preallocating disk space to files.
Basically, I want a equivilent to posix_fallocate or the ever wonderful xfsctl XFS_IOC_RESVSP64 call.
The idea being to (quickly) create a large file on disk that is stored efficiently (i.e. isn’t fragmented).
From SQL, you’d do something like “CREATE LOGFILE GROUP lg1 ADD UNDOFILE ‘uf1′ INITIAL_SIZE 1G;” and expect a 1GB file on disk. One way of getting this is calling write() (or WriteFile() on Win32) repeatedly until you’ve written a 1GB file full of zeros. This means you’re generating approximately 1GB of IO.
Except it’s worse than that: every time you extend the file,[Read more...]
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