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Showing entries 1 to 10 of 57 10 Older Entries

Displaying posts with tag: primary (reset)

GHOST vulnerability (CVE-2015-0235) Percona response
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Cloud security company Qualys announced Tuesday the issues prevalent in glibc since version 2.2 introduced in 2000-11-10 (the complete Qualys announcement may be viewed here). The vulnerability, CVE-2015-0235, has been dubbed “GHOST.”

As the announcement from Qualys indicates, it is believed that MySQL and by extension Percona Server are not affected by this issue.

Percona is in the process of conducting our own review into the issue related to the Percona Server source code – more information will be released as …

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Multi-threaded replication with MySQL 5.6: Use GTIDs!
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MySQL 5.6 allows you to execute replicated events in parallel as long as data is split across several databases. This feature is named “Multi-Threaded Slave” (MTS) and it is easy to enable by setting slave_parallel_workers to a > 1 value. However if you decide to use MTS without GTIDs, you may run into annoying issues. Let’s look at two of them.

Skipping replication errors

When replication stops with an error, a frequent approach is to “ignore now and fix later.” This means you will run SET GLOBAL sql_slave_skip_counter=1 to be able to restart replication as quickly as possible and …

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MySQL benchmarks on eXFlash DIMMs
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In this blog post, we will discuss MySQL performance on eXFlash DIMMs. Earlier we measured the IO performance of these storage devices with sysbench fileio.

Environment

The benchmarking environment was the same as the one we did sysbench fileio in.

CPU: 2x Intel Xeon E5-2690 (hyper threading enabled)
FusionIO driver version: 3.2.6 build 1212
Operating system: CentOS 6.5
Kernel version: 2.6.32-431.el6.x86_64

In this case, we used a separate machine for testing which had a 10G ethernet …




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Using Percona Cloud Tools to solve real-world MySQL problems
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For months when speaking with customers I have been positioning Percona Cloud Tools (PCT) as a valuable tool for the DBA/Developer/SysAdmin but only recently have I truly been able to harness the data and make a technical recommendation to a customer that I feel would have been very difficult to accomplish otherwise.

Let me provide some background: I was tasked with performing a Performance Audit for one of …

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Importing big tables with large indexes with Myloader MySQL tool
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Mydumper is known as the faster (much faster) mysqldump alternative. So, if you take a logical backup you will choose Mydumper instead of mysqldump. But what about the restore? Well, who needs to restore a logical backup? It takes ages! Even with Myloader. But this could change just a bit if we are able to take advantage of Fast Index Creation.

As you probably know, Mydumper and mysqldump export the struct of a table, with all the indexes and the constraints, and of course, the data. Then, Myloader and MySQL import the struct of the table and import the data. The most important difference is that you can configure Myloader to …

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Identifying useful info from MySQL row-based binary logs
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As a MySQL DBA/consultant, it is part of my job to decode the MySQL binary logs – and there are a number of reasons for doing that. In this post, I’ll explain how you can get the important information about your write workload using MySQL row-based binary logs and a simple awk script.

First, it is important to understand that row-based binary logs contain the actual changes done by a query. For example, if I run a delete query against a table, the binary log will contain the rows that were deleted. MySQL provides the mysqlbinlog utility to decode the events stored in MySQL binary logs. You can read more about …

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Looking deeper into InnoDB’s problem with many row versions
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A few days ago I wrote about MySQL performance implications of InnoDB isolation modes and I touched briefly upon the bizarre performance regression I found with InnoDB handling a large amount of versions for a single row. Today I wanted to look a bit deeper into the problem, which I also filed as a bug.

First I validated in which conditions the problem happens. It seems to happen only in REPEATABLE-READ isolation mode and only …

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Hyper-threading – how does it double CPU throughput?
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The other day a customer asked me to do capacity planning for their web server farm. I was looking at the CPU graph for one of the web servers that had Hyper-threading switched ON and thought to myself: “This must be quite a misleading graph – it shows 30% CPU usage. It can’t really be that this server can handle 3 times more work?”

Or can it?

I decided to do what we usually do in such case – I decided to test it and find out the truth. Turns out – there’s more to it than meets the eye.

How Intel Hyper-Threading works

Before we get to my benchmark results, …


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MySQL performance implications of InnoDB isolation modes
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Over the past few months I’ve written a couple of posts about dangerous debt of InnoDB Transactional History and about the fact MVCC can be the cause of severe MySQL performance issues. In this post I will cover a related topic – InnoDB Transaction Isolation Modes, their relationship with MVCC (multi-version concurrency control) and how they impact MySQL performance.

The …

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Django with time zone support and MySQL
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This is yet another story of Django web-framework with time zone support and pain dealing with python datetimes and MySQL on the backend. In other words, offset-naive vs offset-aware datetimes.

Shortly, more about the problem. After reading the official documentation about the time zones, it makes clear that in order to reflect python datetime in the necessary time zone you need to make it tz-aware first and than show in that time zone.

Here is the first issue: tz-aware in what time …

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Showing entries 1 to 10 of 57 10 Older Entries

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