Oreilly Webcast 01 19 10
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DRBD & MySQL An HA Match Made In Heaven
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Transcript of Oreilly Webcast 01 19 10
DRBD & MySQL
An HA Match Made In Heaven
April 10, 2023 •• Sean Hull •• <[email protected]>
2
What is DRBD?
Distributed replicated block device
Sits between filesystem & hardware dev
Software-based mirroring
April 10, 2023 •• Sean Hull •• <[email protected]>
3
HA with MySQL Replication
Fast & easy setupStatement based problemsNon-deterministic functionsAsynchronous - time lagRequires monitoring error logMaatkit mk-table-checksum
April 10, 2023 •• Sean Hull •• <[email protected]>
4
HA with MySQL & DRBD
Active/passive clusterExact copy of mysql dbSmall performance hit
using /dev/drbd0 versus /dev/sda1
April 10, 2023 •• Sean Hull •• <[email protected]>
5
Intro to Sun’s Virtualbox
Supports Mac, Windows, Linux
Simple installerBuild VMs easilyAdd virtual external disks
April 10, 2023 •• Sean Hull •• <[email protected]>
6
Downloads
Virtualboxvirtualbox.org/wiki/Downloads
CentOSwiki.centos.org/Download
April 10, 2023 •• Sean Hull •• <[email protected]>
7
Create Your VMs
Create vm using GUI User Storage tab - Add 2nd disk - 25m
scsi Config networking interface
Bridged adaptor Download CentOS DVD ISO image Use storage tab - select ISO image Start VM running - boot iso dvd Install CentOS 5.4 Edit /etc/hosts file
April 10, 2023 •• Sean Hull •• <[email protected]>
8
Install DRBD on Both Nodes$ yum install drbd$ yum install kmod-drbd$ yum install emacs
April 10, 2023 •• Sean Hull •• <[email protected]>
9
Configure DRBD
Edit drbd.conf common { protocol C; } resource sean { on adelie { device /dev/drbd0; disk /dev/sda1; meta-disk internal; address 192.168.0.106:7789; } on african { device /dev/drbd0; disk /dev/sda1; meta-disk internal; address 192.168.0.105:7789; } }
April 10, 2023 •• Sean Hull •• <[email protected]>
10
Protocol C?
C - write IO is reported as completed, if we know it has reached _both_ local & remote DISK for critical transactional data.
B - write IO is reported as completed, if it has reached local DISK and remote buffer cache. for most cases.
A - write IO is reported as completed, if it has reached local DISK and local tcp send buffer. for high latency networks
benchmarks have shown that C is actually better than B.
April 10, 2023 •• Sean Hull •• <[email protected]>
11
What is meta-disk?
Drbd stores metadataInternal - end of your volumeExternal - /dev/hda3…Swapping hd is slightly
different
April 10, 2023 •• Sean Hull •• <[email protected]>
12
Start DRBD Be sure iptables is stopped
$ /etc/init.d/iptables stop $ fdisk /dev/sda $ drbdadm create-md sean $ /etc/init.d/drbd start $ drbdadm -- --overwrite-data-of-peer
primary sean $ watch cat /proc/drbd $ mkfs.ext3 /dev/drbd0 $ mount /dev/drbd0 /mnt/mysql
April 10, 2023 •• Sean Hull •• <[email protected]>
13
Configure MySQL & Start
$ yum install mysql-server.x86_64
Edit /etc/my.cnfdatadir=/mnt/mysql
$ mysql_install_db$ mysqld_safe &Login & create test.demo_tbl
April 10, 2023 •• Sean Hull •• <[email protected]>
14
Test Switching Nodes
On adelie do:Stop mysql$ umount /mnt/mysql
On african do:$ drbdadm primary sean$ mount /dev/drbd0 /mnt/mysql$ mysqld_safe &
April 10, 2023 •• Sean Hull •• <[email protected]>
15
Using Heartbeat
/etc/ha.d/ha.cf/etc/ha.d/haresources/etc/ha.d/authkeysStop mysqlumount /mnt/mysql$ /etc/init.d/heartbeat start/var/log/heartbeat-debug.log
April 10, 2023 •• Sean Hull •• <[email protected]>
16
The Whole HA Stack
drbd - mirror fs, software SANmysql - built on drbd volumeHeartbeat
LvsVirtual IPStart, stop servicesheartbeat
April 10, 2023 •• Sean Hull •• <[email protected]>
17
Conclusions
Alternative to MySQL Repl.Requires some sysadmin
skillsCombined with Heartbeat
Automatic failoverVirtual IP address for both
servers
April 10, 2023 •• Sean Hull •• <[email protected]>
18
Further Reading
ProMySQL: Kruckenberg& Pipes
High Perf MySQL: Lentz, Zaitsev, Tkachenko, Sawodny, Balling, Schwartz
mysqlperformanceblog.complanetmysql.com
