… simple copy operation from MySQL data directory will result in a total disaster after MySQL stops responding to…cfq” > /sys/block/$device/queue/scheduler ; fi ; done # cat /sys/block/sd?/queue/scheduler noop anticipatory deadline [cfq] noop anticipatory deadline [cfq] noop anticipatory deadline [cfq…
Post: Linux IO Schedulers and MySQL
January 30, 2007 By 7 Comments
… ago “AS” scheduler could be several times slower than deadline for MySQL workloads such as SysBench or DBT2 when it went down… to see the difference. From the article it looks like CFQ should be good choice for databases and it is also… docs it is mentioned it uses “per process” scheduling while MySQL is single process but single thread – does each thread gets…
Post: Linux schedulers in tpcc like benchmark
January 30, 2009 By 19 Comments
… that IO scheduler CFQ coming by default in RedHat / CentOS 5.x may be not so good for MySQL. And yesterday one customer reported that just changing cfq to noop solved their InnoDB IO… disks in RAID10, controller Perc/6i with BBU) to compare cfq, deadline, noop and anticipatory (last one just to get number, I…
Comment: Living with backups
November 18, 2008 By 28 Comments
…* dd (Idle class) and MySQL (default class) to slow down to ridiculously low speed! – Using the deadline scheduler (which was the default… fast and MySQL starts lagging slightly. – Using CFQ with default class, side read operation is about twice as fast while MySQL replication is… still a bit faster than using deadline, and MySQL is lagging behind significantly more than using deadline. The IO subsystem is a hardware…
Comment: Living with backups
July 1, 2009 By 28 Comments
… with CFQ, and as I point out in that post, even when using IO classes to give priority to MySQL, CFQ makes MySQL run slower than Deadline on my hardware. I haven’t tested with… it should be even worse by design; Anticipatory should make Mysql wait even more on IO expecting sequential reads; while it…
Comment: Linux schedulers in tpcc like benchmark
February 4, 2009 By 19 Comments
I used Deadline with MySQL for many years… Recently I wanted to test the CFQ Idle class for an IO-intensive job running….24 kernels I even experienced a bug in which both MySQL and the job were running ridiculously slow with barely no… RAID. Might be different for other subsystems, but for be deadline just rocks, even without BBU (6-drive Raid10 though)
Post: FlashCache: tpcc workload
May 25, 2010 By 18 Comments
… off power on SSD drive in the middle of tpcc-mysql run, just SSD power, not whole server. No wonder FlashCache… after restart FlashCache was able to attach previous cache, and MySQL was able to start and finish crash recovery. I am… team reads this post – please change default IO scheduler from CFQ to Deadline. Seriously, it makes so much damage on performance on…
Post: Performance impact of complex queries
January 17, 2007 By 11 Comments
What is often underestimated is impact of MySQL Performance by complex queries on large data sets(ie some … your normal working set from OS cache. Operation Systems and MySQL Itself employs various strategies to attempt to minimize such effect… for directory with couple of files. In recent Linux Kernels deadline or cfq IO schedulers should be better with this. So what…
