Confessions of a DBA: worst and best things I've

done in productionEmily Slocombe

Open Source Bridge 2014

High and Low lights:• at it since 1999!

• I’ve used the blackhole storage engine a few awesome times

• I’ve seriously broken things

• I’ve confessed breaking things to rather famous mysql people

• They remember these stories for years

Breaking things = learning

image: http://www.boredpanda.org/lets-see-who-can-post-the-cutest-animal-photo/#post0

Adventures in:• Engine=blackhole

• data migration

• ‘Ghetto RAID’: mistakes in innodb

• the Hammer that is mysqltuner.pl

• MyISAM

• bad and worse

• Benchmarking!

Engine=blackhole

set  sql_log_bin=0;  alter  table  blah  engine=blackhole;

1. Master was for bin logs only on this one table.

2. Slave could not keep up with replication and this giant table with giant text blobs was IO pain!  

image from: http://www.bearlakereserve.com/what-are-our-furry-friends-up-to/

Data Migration

• no sleep for 1 week!

• lived on energy drinks, greek yogurt, and chocolate covered espresso beans.!

• couldn’t eat vegetables for 1 year

ssh tunnel(s)!

Sad, cheap RAID

• 5.1.47 MySQL

• slow disks, long wait for more fast SSD / FC

• 1 SSD

• InnoDB: could symlink folders, not files

Sad, cheap RAID

• I should have tested this.

• BTW: InnoDB is ‘sparse file type’

• oops

I am not a DBA

• mysqltuner.pl seems like a great idea

• max heap / query cache

I am not a DBARECOMMENDATIONS:  version  less  then  5.1,  upgrade!  version  less  then  5.1.30  (the  first  GA  release  of  5.1),  upgrade!  The  MySQL  manual  only  is  accurate  for  official  MySQL  binaries,  Percona  documentation  is  at  http://www.percona.com/docs/wiki/  The  query  cache  is  not  being  fully  utilized.  Increase  query_cache_size  -­‐-­‐  there  are  too  many  low  memory  prunes.  Too  many  sorts  are  causing  temporary  tables.    Consider  increasing\nsort_buffer_size  and/or  read_rnd_buffer_size  There  are  lots  of  rows  being  sorted.    Consider  using  indexes  in  more  queries  to  avoid  sorting  too  often.  There  are  too  many  joins  without  indexes  -­‐-­‐  this  means  that  joins  are  doing  full  table  scans.  The  rate  of  reading  the  first  index  entry  is  high;  this  usually  indicates  frequent  full  index  scans.  The  rate  of  reading  data  from  a  fixed  position  is  high;  this  indicates  many  queries  need  to  sort  results  and/or  do  a  full  table  scan,  including  join  queries  that  do  not  use  indexes.  The  rate  of  reading  the  next  table  row  is  high;  this  indicates  many  queries  are  doing  full  table  scans.  Too  many  temporary  tables  are  being  written  to  disk.    Increase  max_heap_table_size  and  tmp_table_size.  Too  many  intermediate  temporary  tables  are  being  created;  consider  increasing  sort_buffer_size  (sorting),  read_rnd_buffer_size  (random  read  buffer,  ie,  post-­‐sort),  read_buffer_size  (sequential  scan).  MyISAM  key  buffer  (index  cache)  %  used  is  low.    You  may  need  to  decrease  the  size  of  key_buffer_size,  re-­‐examine  your  tables  to  see  if  indexes  have  been  removed,  or  examine  queries  and  expectations  about  what  indexes  are  being  used.  MyISAM  key  buffer  (index  cache)  %  used  is  low.    You  may  need  to  decrease  the  size  of  key_buffer_size,  re-­‐examine  your  tables  to  see  if  indexes  have  been  removed,  or  examine  queries  and  expectations  about  what  indexes  are  being  used.  Size  of  the  table  cache  InnoDB  log  file  size  is  not  an  appropriate  size,  in  relation  to  the  InnoDB  buffer  pool.    Consider  changing  either\ninnodb_log_file_size  or  innodb_buffer_pool_size  

MyISAM

• drupal node table

• nearly read-only

• why not?

MyISAM• 200+G table on EBS

• internally corrupt

• version 5.0.92

• upgrade version

• need to fix table

• add disk space

MyISAM, now InnoDBI’d rather be blaming MyISAM, but I cannot.

MyISAM, now InnoDB

Benchmarking

Breaking things = learning

Emily Slocombe!Twitter: @NinjaBunny_ Work: emily.slocombe@acquia.com

Photocredits: piggie: http://www.boredpanda.org/lets-see-who-can-post-the-cutest-animal-photo/#post0 squirrel: http://www.bearlakereserve.com/what-are-our-furry-friends-up-to/

!Other credits:

mysqltuner.pl: https://launchpad.net/mysqltuner