New stats in iostat

Recelnty I've noticed that iostat (for RedHat sysstat-9.0.4-31 version) reports new fields: r_await and w_await.

Following online documentation: this stands for:

The average time (in milliseconds) for I/O requests issued to the device to be served. This includes the time spent by the requests in queue and the time spent servicing them.

Munin KVM VMs real memory usage plugin

I've got some machines that use KVM as virtualization platform. I monitor then using munin, but I was not able to find munin plugin that shows proper usage of memory by virtual machines. I've found this one, but it shows memory declared for VM in config file (maximum memory value for VM to be honest). So this one is not good if you want to see realtime memory usage.

How to trace ssh tunneled/proxied connections

Almost everyone knows ssh port forward (-L/-R) or dynamic port forward (-D) features. They are very useful. For example when connecting to the internet using hotspot or other free access point it's very good idea to use ssh dynamic port forward. Doing so prevents other users from beeing able to see your traffic.

Why update to newer versions - munin

Ppl tend to not update their software. There is a rule "If something works, do not touch it". But this rule is not true.
Lately I've update munin to version 2.0.19-1, and after checking performance of my kvm nodes I got really surprised. CPU usage for host which is mostly generating munin raports dropped from 23% to about 12%, which means that new version is 2 times faster!!!
All nice cpu usage on the graph is munin.

Another look at amazon EBS storage performance

Lately I've gave up bonnie++ in favor of iozone. I've done lot of performance checks on hardware I've got in my hands. That also means that I have to check iozone performance on my amazon instances.

Since tested instance was t1.micro, 1Gb test file was enough to avoid false cache results.

So command run was:

./iozone -a -i0 -i1 -i2 -r4k -O -n1g -g1g

WordPress: auto add new users to post notification

There is nice plugin for WordPress called "Post Notification" which allows your WP users to be informed about new posts. But those users should subscribe manually using subscribe page (or another plugin, for example: "WordPress Notification Bar"). You can also add new users manually as WP admin, but this is annoying especially if you got loads of new users.

SQL convert interval with days to hh:mm:ss format

Lately I've been dealing with some data from SQL database. I have to count average interval, but the result was in format:

x days xx:xx:xx

and it look just ugly.

Quick look at amazon EBS / instance storage performance

Lately I've been testing amazon EC2 and moving my virtual machines there. So I got a chance to test some EBS / instance storage block devices.

And my t1.micro instance got EBS performance like this:


And as you can see, this performance is not amazing. Slow writes, slow rewrites, nice reads (but still slower then 7200 rpm hdd). So you can't expect fast IO from t1.micro. But what amazes me is seek amount, almost like ssd storage. Strange but true. Of course those results varies on (I guess) resources available.

LUKS and intel aes-ni performance part 2

Lately I've bought laptop with Intel i7-3720QM. Laptop got 2 disks: SSD Vertex 120GB and original WD Scorpio 7200rpm hdd. I have to check LUKS performance of this setup ('cause I use LUKS on daily basis). And it looks like this (of course bonnie++ results):

HT on, WD Scorpio 320GB 7200rpm, lvm, ext4, no encryption:

JBO-30003: The application pool failed ...

Lately I've been troubleshooting "JBO-30003: The application pool failed to checkout an application module" error with Oracle Application Server 10g. The person which reported the error, said that this is definitely server side issue. So I started to debug this problematic java application.

Oracle Metalink and Oracle forums claims that this is DB connection related error. So after dealing with some OC4J different configurations I started to debug this application on OS level.


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by Dr. Radut