I've been using MySql with InnoDb engine for a while and am pretty satisfied with the performance. I got 10 tables and update them twice every second. Recently I had a power outage and was not able to restart the database without setting the innodb_force_recovery to at least 4. But when trying to fix the broken table the database would crash again. I tried optimizing, checking, analyzing and so on, but all resulted in crash. The error log contains messages like:
InnoDB: Error: page 570 log sequence number 7289495 InnoDB: is in the future! Current system log sequence number 5574939.
Eventually I managed to dump the database via mysqldump (with the innodb_force_recovery at 6) after deleting all files related to a specific table. Then I reinstalled xampp and reloaded the dump. This got me up and running again with only one table lost.
My question is this, how can one corrupt table cause the whole database to crash?
Is there a way to minimize the risk of this happening again, some kind of configuration to increase the robustness against power failures? I know the obvious answer is to keep a replicate backup database on a separate server, but being in just the testing phase of the development it seems like overkill.
Here's the configuration file I am using.
# Example MySQL config file for small systems.
#
# This is for a system with little memory (<= 64M) where MySQL is only used
# from time to time and it's important that the mysqld daemon
# doesn't use much resources.
#
# You can copy this file to
# C:/xampp2/mysql/bin/my.cnf to set global options,
# mysql-data-dir/my.cnf to set server-specific options (in this
# installation this directory is C:/xampp2/mysql/data) or
# ~/.my.cnf to set user-specific options.
#
# In this file, you can use all long options that a program supports.
# If you want to know which options a program supports, run the program
# with the "--help" option.
# The following options will be passed to all MySQL clients
[client]
# password = your_password
port = 3306
socket = "C:/xampp2/mysql/mysql.sock"
# Here follows entries for some specific programs
# The MySQL server
[mysqld]
port= 3306
socket = "C:/xampp2/mysql/mysql.sock"
basedir = "C:/xampp2/mysql"
tmpdir = "C:/xampp2/tmp"
datadir = "C:/xampp2/mysql/data"
pid_file = "mysql.pid"
# enable-named-pipe
key_buffer = 16M
max_allowed_packet = 1G
sort_buffer_size = 512K
net_buffer_length = 8K
read_buffer_size = 256K
read_rnd_buffer_size = 512K
myisam_sort_buffer_size = 8M
log_error = "mysql_error.log"
# Change here for bind listening
# bind-address="127.0.0.1"
# bind-address = ::1 # for ipv6
# Where do all the plugins live
plugin_dir = "C:/xampp2/mysql/lib/plugin/"
# Don't listen on a TCP/IP port at all. This can be a security enhancement,
# if all processes that need to connect to mysqld run on the same host.
# All interaction with mysqld must be made via Unix sockets or named pipes.
# Note that using this option without enabling named pipes on Windows
# (via the "enable-named-pipe" option) will render mysqld useless!
#
# commented in by lampp security
#skip-networking
#skip-federated
# Replication Master Server (default)
# binary logging is required for replication
# log-bin deactivated by default since XAMPP 1.4.11
#log-bin=mysql-bin
# required unique id between 1 and 2^32 - 1
# defaults to 1 if master-host is not set
# but will not function as a master if omitted
server-id = 1
# Replication Slave (comment out master section to use this)
#
# To configure this host as a replication slave, you can choose between
# two methods :
#
# 1) Use the CHANGE MASTER TO command (fully described in our manual) -
# the syntax is:
#
# CHANGE MASTER TO MASTER_HOST=<host>, MASTER_PORT=<port>,
# MASTER_USER=<user>, MASTER_PASSWORD=<password> ;
#
# where you replace <host>, <user>, <password> by quoted strings and
# <port> by the master's port number (3306 by default).
#
# Example:
#
# CHANGE MASTER TO MASTER_HOST='125.564.12.1', MASTER_PORT=3306,
# MASTER_USER='joe', MASTER_PASSWORD='secret';
#
# OR
#
# 2) Set the variables below. However, in case you choose this method, then
# start replication for the first time (even unsuccessfully, for example
# if you mistyped the password in master-password and the slave fails to
# connect), the slave will create a master.info file, and any later
# change in this file to the variables' values below will be ignored and
# overridden by the content of the master.info file, unless you shutdown
# the slave server, delete master.info and restart the slaver server.
# For that reason, you may want to leave the lines below untouched
# (commented) and instead use CHANGE MASTER TO (see above)
#
# required unique id between 2 and 2^32 - 1
# (and different from the master)
# defaults to 2 if master-host is set
# but will not function as a slave if omitted
#server-id = 2
#
# The replication master for this slave - required
#master-host = <hostname>
#
# The username the slave will use for authentication when connecting
# to the master - required
#master-user = <username>
#
# The password the slave will authenticate with when connecting to
# the master - required
#master-password = <password>
#
# The port the master is listening on.
# optional - defaults to 3306
#master-port = <port>
#
# binary logging - not required for slaves, but recommended
#log-bin=mysql-bin
# Point the following paths to different dedicated disks
#tmpdir = "C:/xampp2/tmp"
#log-update = /path-to-dedicated-directory/hostname
# Uncomment the following if you are using BDB tables
#bdb_cache_size = 4M
#bdb_max_lock = 10000
# Comment the following if you are using InnoDB tables
#skip-innodb
innodb_data_home_dir = "C:/xampp2/mysql/data"
innodb_data_file_path = ibdata1:10M:autoextend
innodb_log_group_home_dir = "C:/xampp2/mysql/data"
#innodb_log_arch_dir = "C:/xampp2/mysql/data"
## You can set .._buffer_pool_size up to 50 - 80 %
## of RAM but beware of setting memory usage too high
innodb_buffer_pool_size = 2G
innodb_additional_mem_pool_size = 16M
## Set .._log_file_size to 25 % of buffer pool size
innodb_log_file_size = 50M
innodb_log_buffer_size = 20M
innodb_flush_log_at_trx_commit = 2
innodb_lock_wait_timeout = 50
innodb_buffer_pool_instances = 4
## UTF 8 Settings
#init-connect=\'SET NAMES utf8\'
#collation_server=utf8_unicode_ci
#character_set_server=utf8
#skip-character-set-client-handshake
#character_sets-dir="C:/xampp2/mysql/share/charsets"
[mysqldump]
quick
max_allowed_packet = 16M
[mysql]
no-auto-rehash
# Remove the next comment character if you are not familiar with SQL
#safe-updates
[isamchk]
key_buffer = 20M
sort_buffer_size = 20M
read_buffer = 2M
write_buffer = 2M
[myisamchk]
key_buffer = 20M
sort_buffer_size = 20M
read_buffer = 2M
write_buffer = 2M
[mysqlhotcopy]
interactive-timeout
InnoDB is very conservative when it comes to data consistency. If it catches anything unexpected (wrong checksum, header value, anything) it intentionally crashes in order not to damage data.
How "to minimize the risk of this happening again"?
The best is to keep safe defaults of innodb_flush_log_at_trx_commit, doublewrite, etc. Internet is full of thoughtless advices on "how to make MySQL faster", but it comes with price, you know.