One of the very frequent cases with performance problems with MySQL is what they happen every so often or certain times… need to know it is not MySQL problem, might be even not problem with your MySQL configuration, queries and hardware, even though… push concurrency too high Many developers will test script with multiple level of concurrency and find out doing work from 32…
Post: Join Optimizations in MySQL 5.6 and MariaDB 5.5
April 4, 2012 By 2 Comments
…, then worst case you could be reading the same page multiple times into the buffer pool. So considering this drawback, Batched… that the disks are 4 5.4K disks in Software RAID5. Also note that the following changes were made on MySQL 5.6… disk 2.2G vs 5G. However, there is one number in MariaDB 5.5 that is quite large as compared to MySQL…
Post: Aligning IO on a hard disk RAID – the Theory
June 9, 2011 By 15 Comments
… RAID is perfectly aligned to disk sectors (again due to the fact operations are done in multiples of 512-bytes), outside of… so in these cases there would be fewer pages spanning multiple disks so the effects of misalignment would be less significant. Here…’s no striping, with RAID0 number of bearing disks is actual number of disks (N), with RAID1+0 (RAID10) it’s N…
Post: How multiple disks can benefit for single client workload ?
April 26, 2008 By 4 Comments
… is IO bound or CPU bound, while to understand if MySQL goes through more rows than it needs to requires look… by the thread and so can result in multiple outstanding requests to the disk. Though this does not help dramatically for many…. Let us get back to multiple outstanding IOs case – Matt points out the issue of disk contention people constantly forgot about. If…
Post: Jeremy Cole on MySQL Replication
May 27, 2006 By 12 Comments
… which make certain disks to flush their cache. Watch out for MySQL 5.0 – if you enabled Binary log with MySQL 5.0 you loose group commit which can dramatically increase commit rate for multiple user load. See… you have multiple disks they will not be used effectively as replication SQL thread will typically submit IO requests to the disk one…
Post: Getting MySQL Core file on Linux
August 26, 2011 By 1 Comment
… you should consider two things – disk space and restart time. The core file will dump all MySQL Server memory content including buffer… be looking at many times the amount of memory MySQL consumes worth of disk space. You have to do couple of changes…/lib/mysql (datadir) on my system (Ubuntu). You might be lucky and it might work in your system. I also enable multiple…
Post: MySQL caching methods and tips
April 4, 2011 By 4 Comments
…, but the key recently expired. The stampede impacts performance because multiple requests try to recompute the contents at the same time… unpredictable performance of the MySQL query cache, since the rate of invalidation can not be controlled, and multiple cache entries may be… data usually face two bottlenecks: disk IO and CPU usage. Disk IO is expensive, and even if the disk bottleneck is eliminated, the…
Post: Why MySQL could be slow with large tables ?
June 9, 2006 By 139 Comments
… row which means you get about 100 rows/sec. Note multiple drives do not really help a lot as we’re…, which is completely disk bound can be very slow. One of the reasons elevating this problem in MySQL is lack of advanced… have whole bunch of problems solved just doing so. Use multiple servers to host portions of data set. Store portion of…
Post: Why you should ignore MySQL's key cache hit ratio
February 28, 2010 By 27 Comments
… which is a worst-case scenario for spinning disks. This is also very hard to prove, … are many subtleties including the possibility of having multiple key caches. But I’ll give the simple…the results to your IO system’s capabilities. MySQL doesn’t have good instrumentation for scientifically choosing…
Post: How InnoDB handles REDO logging
February 3, 2011 By 18 Comments
… in the log needs to be able to be redone multiple times since at restart and media recovery we will not… the log to disk at commit. By this means you are ensuring that in the event of a MySQL crash the data… REDO logging and the checkpoint on disk. Vadim touched upon this subject recently in his post MySQL 5.5.8 – in…
