3 ways MySQL uses indexes
I often see people confuse different ways MySQL can use indexing, getting wrong ideas on what query performance they should expect. There are 3 main ways how MySQL can use the indexes for query execution, which are not mutually exclusive, in fact some queries will use indexes for all 3 purposes listed here. Using index to find rows The main purpose of the index is to find rows quickly – without sc
Percona Toolkit 2.1 with New Online Schema Change Tool
I’m proud to announce the GA release of version 2.1 of Percona Toolkit. Percona Toolkit is the essential suite of administrative tools for MySQL. With this release we introduce a new version of pt-online-schema-change, a tool that enables you to ALTER large tables with no blocking or downtime. As you know, MySQL locks tables for most ALTER operations, but pt-online-schema-change performs the ALTER
Identifying the load with the help of pt-query-digest and Percona Server
OverviewProfiling, analyzing and then fixing queries is likely the most oft-repeated part of a job of a DBA and one that keeps evolving, as new features are added to the application new queries pop up that need to be analyzed and fixed. And there are not too many tools out there that can make your life easy. However, there is one such tool, pt-query-digest (from Percona Toolkit) which provides you
When EXPLAIN estimates can go wrong!
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Multiple MySQL instances on Fusion-io ioDrive
It is known that MySQL due internal limitations is not able to utilize all CPU and IO resources available on modern hardware. Idea is to run multiple instances of MySQL to gain better performance on Fusion-io ioDrive card. Full report is available in PDF For tests we used tpcc-mysql package, which generates TPCC-like workload on MySQL systems. Server hardware: Dell PowerEdge R815 Storage: Fusion-i
Disaster: MySQL 5.5 Flushing
We raised topic of problems with flushing in InnoDB several times, some links: InnoDB Flushing theory and solutions MySQL 5.5.8 in search of stability This was not often recurring problem so far, however in my recent experiments, I observe it in very simple sysbench workload on hardware which can be considered as typical nowadays. Hardware: HP ProLiant DL380 G6, with 72GB of RAM and RAID10 on 8 di
Is VoltDB really as scalable as they claim?
Before I begin, a disclaimer. VoltDB is not a customer, and did not pay Percona or me to investigate VoltDB’s scalability or publish this blog post. More disclaimers at the end. Short version: VoltDB is very scalable; it should scale to 120 partitions, 39 servers, and 1.6 million complex transactions per second at over 300 CPU cores, on the benchmarked configuration, with the recommended level of
How to use tcpdump on very busy hosts
Often I run into problems when trying to use mk-query-digest with tcpdump on “very” busy hosts. You might be thinking, “very busy is a relative and unquantifiable term,” and you’d be right, so I’ll phrase this differently. Let me give a little background to the problem first. Mk-query-digest tries to handle dropped or missing packets gracefully, but even so they can skew results dramatically. Imag
Estimating Replication Capacity
It is easy for MySQL replication to become bottleneck when Master server is not seriously loaded and the more cores and hard drives the get the larger the difference becomes, as long as replication remains single thread process. At the same time it is a lot easier to optimize your system when your replication runs normally – if you need to add/remove indexes and do other schema changes you probabl
Write performance on Virident tachIOn card
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FusionIO - time for benchmarks
I posted about FusionIO couple times RAID vs SSD vs FusionIO and Testing FusionIO: strict_sync is too strict…. The problem was that FusionIO did not provide durability or results were too bad in strict mode, so I lost interest FusionIO for couple month. But I should express respect to FusionIO team, they did not ignore problem, and recently I was told that in last drivers FusionIO provides durab
MySQL 5.5.8 and Percona Server on Fast Flash card (Virident tachIOn)
This is to follow up on my previous post and show the results for MySQL 5.5.8 and Percona Server on the fastest hardware I have in our lab:Â a Cisco UCS C250 server with 384GB of RAM, powered by a Virident tachIOn 400GB SLC card. To see different I/O patterns, I used different innodb_buffer_pool_size settings: 13G, 52G, an 144G on a tpcc-mysql workload with 1000W (around 100GB of data). This combi
Ultimate MySQL variable and status reference list
I am constantly referring to the amazing MySQL manual, especially the option and variable reference table. But just as frequently, I want to look up blog posts on variables, or look for content in the Percona documentation or forums. So I present to you what is now my newest Firefox toolbar bookmark: an option and variable reference for all three sites in one! abort_slave_event_count blog perc
How long is recovery from 8G innodb_log_file
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Impact of the number of idle connections in MySQL (version 2)
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XtraDB benchmarks - 1.5X gain in IO-bound load
All of Percona’s open-source software products, in one place, to download as much or as little as you need.
Performance gotcha of MySQL memory tables
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