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What’s a good buffer pool read/write ratio?

Abidoon — Tue, 31 May 2011 15:05:51 +0000

At Percona Live last week, someone showed me a graph from their Cacti monitoring system, using the templates that I wrote. It was the buffer pool pages read, written, and created. He asked me if the graph was okay. Shouldn’t there be a lot more pages read than written, he asked? It’s a great question.

I’ve blogged before about the danger of trying to interpret ratios. Ratios are not good ways to discover whether systems are healthy. So, why graph them, then?

First, let me say that the graph actually doesn’t show a ratio — it just shows the absolute values of the reads, writes, and creates per second, stacked on top of each other. The person was mentally comparing them and creating a ratio from them. But there’s no ratio on the graph itself:

Regardless of that, some systems ought to have more reads than writes, and vice versa. So if you’re looking at your graph wondering what it should look like, the answer is probably “it should look exactly as it looks!”

I’ve gotten a lot of questions over time about how to interpret the Cacti graphs, and this person helped me to understand what the questions were really about. People were asking me “when I look at these graphs, how can I tell if anything is wrong with my system?” But that’s not really the most useful way to approach the graphs.

It really comes down to the difference between discovery and diagnosis. In general, it’s best to use the graphs for diagnosing problems that you already know about, not for trying to discover problems. Your monitoring and alerting system (Nagios?) should be trying to discover whether there is a problem. The graphs are there for quickly showing you what has changed. If the website suddenly starts responding very slowly, for example, then you can look at the graphs and see if any of them have sharp increases or decreases. You can use that information to help you diagnose.

But in general, I wouldn’t spend very much time looking at the graphs from day to day. I’d just check them once in a while — maybe once a week I’d look at the monthly view — to see if there were any sharp changes during the past week; I’d ensure that I know why those changes happened if I see any (maybe I deployed a new release); and I’d want to make sure that the graphs are still working, and haven’t gotten broken due to some problem like privileges or firewall rules.

In the ideal world, I’d like to simply collect everything, and not even define any graphs for the metrics. Then I’d like an easy way to make graphs on an ad-hoc basis. But Cacti is designed to have defined graphs, and that makes it tempting for people to spend a lot of time looking at them

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ONLINE ONLY: Richard Stallman – No censorship is good censorship

Abidoon — Mon, 20 Sep 2010 19:33:33 +0000

ONLINE ONLY: Richard Stallman – No censorship is good censorship
Free software and GNU movement founder, Richard Stallman, is a legend in certain IT circles. He spoke to DAVID RAMLI about why he dislikes the PR industry and how pornography with 16-17 year olds isnât always child porn.

Linux: A Few Good Reasons to Make the Switch

Abidoon — Tue, 03 Aug 2010 07:14:35 +0000

Linux can reduce your company’s TCO. The bottom line is always important and reducing the total cost of ownership of your computer is always a good thing. One of the reasons Linux TCO is less is because most of the software for Linux is free. In a typical office setting, software vendors such as Microsoft like to update their products once a year or so. If you choose not to buy the newer version, then at some point the software vendor will usually render the old software incompatible with the new version. This puts the company using the software into a tough spot. Buy the new stuff or use the old, incompatible version.

This upgrade or die game is not an issue with Linux. There is no real advantage for, say, Open Office, to make upgrades that render former versions obsolete. Here, the end-user experience is foremost in the developers mind, not on how can we generate more revenue.

So how does a Linux software company make money? Usually with paid support options. Large companies obtain and use Linux and Open Office for free, but will need paid support and training as with paid for software.

Linux is also a great alternative because it runs quite well on older hardware. Again, while paid-for, non-free software is constantly (oftentimes needlessly) growing larger and pushing the limits of current hardware, so that buying new software usually means having to buy new hardware to use it, Linux runs quite happily on just about any old computer running XP. The non-free software vendors tend to upgrade often whether the software is actually getting better or not. Just add something new so we can charge for it. And by all means make it very hardware and cpu intensive so end-users will be forced to upgrade hardware as well. It’s a vicious cycle in the Windows world. Not so in Linux.

Most would-be Linux converts complain that there just isn’t any software for Linux. There is a ton of great software for Linux. Is there Photoshop? No. Excel? No. Word? No. But Linux has excellent alternatives to just about everything. There really isn’t much a Linux computer can’t do. The Gimp is an excellent, advanced image editing package that while not as featured as Photoshop, really gives it a run for its money. For 3D, there’s Blender. Open Office is a great Word and Excel replacement. Open Office can open and edit most Word and Excel documents.

Brett writes on a variety of topics including computers, cooking and adjustable safety razors.

SMPlayer and GNOME Mplayer – Two Incredibly Good Mplayer Based Media Players For

Abidoon — Tue, 20 Jul 2010 02:30:56 +0000

SMPlayer and GNOME Mplayer – Two Incredibly Good Mplayer Based Media Players For
Tech Drive-in: “If you like mplayer, you will love SMPlayer and Gnome-Mplayer. Both SMplayer and Gnome-Mplayer are really good MPlayer front-ends and they do work great”

Is Fedora very good Linux distro for me to use?

Abidoon — Mon, 12 Jul 2010 00:44:49 +0000

all night long
Just looking for a good Gnome distro with up-to-date packages.

Is it a good idea to install Fedora 13 beta?

Abidoon — Fri, 09 Jul 2010 14:30:22 +0000

I’m not a developer, but is the beta generally stable, ie. won’t crash 95% of the time?

Would PHP and MySQL for dummies be a good first way to pick up a scripting language?

Abidoon — Tue, 06 Jul 2010 18:16:53 +0000

I know absolutely no scripting languages… I am dying to pick one up. Would PHP be a good way to start learning scripting, or would there be a better language to pick up as a first language? Thanks a million. I will def. pick a best answer for whoever can explain what and why I should learn it. Thank you!

Tim Minchin – The Good Book (Live)

Abidoon — Sun, 04 Jul 2010 21:45:48 +0000

Tim Minchin is as brilliant and hilarious as ever as he satires the bible in “The Good Book.” I own nothing, obviously, go buy the DVD as Tim Minchin deserves the moolah. BTW, there’s another version on here too (and he should get credit, as he uploaded the video first). Check it out: www.youtube.com

PHP: The Good Parts: Delivering the Best of PHP

Abidoon — Wed, 30 Jun 2010 04:47:08 +0000

ISBN13: 9780596804374
Condition: NEW
Notes: Brand New from Publisher. No Remainder Mark.

Product Description
Get past all the hype about PHP and dig into the real power of this language. This book explores the most useful features of PHP and how they can speed up the web development process, and explains why the most commonly used PHP elements are often misused or misapplied. You’ll learn which parts add strength to object-oriented programming, and how to use certain features to integrate your application with databases. Written by a longtime member of the PHP community, … More >>

PHP: The Good Parts: Delivering the Best of PHP

Ashton Shepherd – Sounds So Good

Abidoon — Sat, 19 Jun 2010 15:21:10 +0000