Recently I had the opportunity to test a storage device from ScaleFlux called CSD 2000. In this blog post, I will share the results of using it to run MySQL in comparison with an Intel device that had a similar capacity.

First of all, why do we need another storage device? Why is ScaleFlux any different?

The answer is simple; it gives us built-in compression and atomic writes. For many workloads, but especially for database-type workloads, these are very important features.

Because of built-in compression, we can store more data on the ScaleFlux device than on a similar device with the same capacity.

Because of atomic writes, we can disable InnoDB Double Write buffer which means less writes/fsync on the disk layer. This should give us a performance advantage against non-atomic drives.

I ran many different tests on different data sizes, with different …

The innodb_io_capacity and innodb_io_capacity_max are often misunderstood InnoDB parameters. As consultants, we see, at least every month, people setting this variable based on the top IO write specifications of their storage. Is this a correct choice? Is it an optimal value for performance? What about the SSD/Flash wear leveling?

Innodb_io_capacity 101

Let’s begin with what the manual has to say about innodb_io_capacity:

“The innodb_io_capacity variable defines the number of I/O operations per second (IOPS) available to InnoDB background tasks, such as flushing pages from the buffer pool and merging data from the change buffer.“

What does this mean exactly? …

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While preparing a post on the design of ZFS based servers for use with MySQL, I stumbled on the topic of fsync call performance. The fsync call is very expensive, but it is essential to databases as it allows for durability (the “D” of the ACID acronym).

Let’s first review the type of disk IO operations executed by InnoDB in MySQL. I’ll assume the default InnoDB variable values.

The first and most obvious type of IO are pages reads and writes from the tablespaces. The pages are most often read one at a time, as 16KB random read operations. Writes to the tablespaces are also typically 16KB random operations, but they are done in batches. After every batch, fsync is called on the tablespace file handle.

To avoid partially written pages in the tablespaces (a source of data corruption), InnoDB performs a doublewrite. During a doublewrite operation, a batch of dirty pages, from 1 to about 100 pages, is …

In this blog post, we’ll look at how ioping can be used with other tools to understand and troubleshoot storage performance, specifically as it relates to MySQL workloads.

I recently ran into ioping, a nice little utility by Konstantin Khlebnikov that checks storage latency.  

For me, the main beauty of ioping is its simplicity and familiarity. It takes after the ubiquitous ping tool, but “pings” the storage instead of the network device.

First, let’s talk about what this tool isn’t: it isn’t a benchmark tool to stress load your storage as heavily as possible. For that, you can use iozone or sysbench (among many others). This also isn’t a tool for looking at …

In this blog post, I will look at disk utilization and saturation.

In my previous blog post, I wrote about CPU utilization and saturation, the practical difference between them and how different CPU utilization and saturation impact response times. Now we will look at another critical component of database performance: the storage subsystem. In this post, I will refer to the storage subsystem as “disk” (as a casual catch-all). 

The most common tool for command line IO performance monitoring is

iostat

, which shows information like this:

root@ts140i:~# iostat -x nvme0n1 5
Linux 4.4.0-89-generic (ts140i)         08/05/2017      _x86_64_        (4 CPU)
avg-cpu:  %user   %nice %system %iowait  %steal   %idle
          0.51    0.00    2.00    9.45    0.00   88.04
Device:         rrqm/s   wrqm/s …

In this blog, we will provide answers to the Q & A for the MySQL In the Cloud: Migration, Best Practices, High Availability, Scaling webinar.

First, we want to thank everybody for attending the June 7, 2017 webinar. The recording and slides for the webinar are available here. Below is the list of your questions that we were unable to answer during the webinar:

How does Percona XtraDB cluster work with AWS for MySQL clustering?

…

In this blog post, I’ll take a look at the performance of the Samsung 960 Pro SSD NVME.

First, I know the Samsung 960 Pro is a consumer SSD NVME drive, not intended for sustained data center workloads. But the AnandTech review looked good enough that I decided to take it for a test spin to see if it would work well with MySQL benchmarks.

Before that, I decided to do a simple sysbench file IO test to see how the drives handled sustained workloads, and if it would start acting up.

My expectation for a consumer SSD drive is that its write consistency will suffer. Many of those drives can sustain high bursts for short periods of time but have to slow down to keep up with write leveling (and other …

In this blog post, I’ll look at the types of NVMe flash health information you can get from using the NVMe command line tools.

Checking SATA-based drive health is easy. Whether it’s an SSD or older spinning drive, you can use the

smartctl

 command to get a wealth of information about the device’s performance and health. As an example:

root@blinky:/var/lib/mysql# smartctl -A /dev/sda
smartctl 6.5 2016-01-24 r4214 [x86_64-linux-4.4.0-62-generic] (local build)
Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org
=== START OF READ SMART DATA SECTION ===
SMART Attributes Data Structure revision number: 16
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
 1 Raw_Read_Error_Rate     0x002f   100   100   000 …

In this blog post we’ll look at how to move a MySQL partition from one table to another, for MySQL versions before 5.7.

Up to version 5.7, MySQL had a limitation that made it impossible to directly exchange partitions between partitioned tables. Now and then, we get questions about how to import an .ibd for use as a partition in a table, as well as how to exchange partitions with another partitioned table. Below is step-by-step instructions on how to move a partition from one table to another.

In this example, one of our customers had two tables with the following structures:

CREATE TABLE live_tbl (
some_id bigint(20) NOT NULL DEFAULT '0',
summary_date date NOT NULL,
PRIMARY KEY (some_id,summary_date)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci
/*!50500 PARTITION BY RANGE …