General Solaris topics

Basic ZFS example

May 2, 2009 by Gleb Reys 1 Comment

I just couldn’t wait any longer, and decided to try something with ZFS. And what do you know? I’ve found a very useful advice from Ben Rockwood, which allows us use regular files created with mkfile as virtual disks for ZFS. VERY useful, especially when you really want to play with such a great technology and maybe try various configurations, but there are no spare physical disks for such experiments.

I will, of course, read and understand all the inner workings of ZFS later, but the first impression of it is this – too easy to be true! 🙂

[Read more…] about Basic ZFS example

Passing command line parameters to DTrace scripts

May 2, 2009 by Gleb Reys 1 Comment

When you’re writing a DTrace script, often you’d like to pass some parameter in command line. Such an easy task might be really hard unless you read a docs.sun.com section about DTrace scripting, particularly a section about command line parameters macros.

As with sh or bash, you can access command line parameters via $0..$9 macroses. But there’s a catch. Values of these macroses should match a certain definition – a number, an identifier or a string. If there isn’t a match here, you’ll get an error.

Let’s start with a simple script. [Read more…] about Passing command line parameters to DTrace scripts

Solaris 10 zones: part one – a working example

May 2, 2009 by Gleb Reys 14 Comments

Many of you have already heard about Solaris 10 zones – it’s a virtualization technology which allows you to create isolated and secure environments for running applications. For end-users these environments look just like separate abstract machines with Solaris 10 installed on them. Inside each zone, all the processes don’t see anything happening in all the other zones on a system. Isolation is done on such a level that processes of one zone can’t see or affect processes of any other zone.

All of this is done on a software level, and by default every Solaris 10 machine has a global zone – only from this zone you can view processes of all the rest zones on your system. You probably didn’t even notice, but upon the completion of your Solaris 10 install, you’re immediately put into the global zone. It’s very easy to see this zone:

solaris# zoneadm list -vc
ID NAME             STATUS         PATH
0 global           running        /

DTrace: Aggregations

May 2, 2009 by Gleb Reys 1 Comment

Quite often it is more important for you to see the whole picture, rather than to know each case when a particular probe fires. For instance, observing a process which consumes a lot of CPU time according to prstat, we ask ourselves: what is this process doing? And often we think about the overall number of system calls executed by this process, and not every particular one of these system calls.

DTrace aggregations are created specifically for answering such questions. Working with sets of numerical data, aggregation functions help us to easily determing average, min and max values of data sets, count numbers and sums of elements in these data sets, and even build frequency distributions.

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DTrace: $target macro variable

May 2, 2009 by Gleb Reys 1 Comment

Macro variables are meant to make your life MUCH easier when scripting with DTrace. Names of such variables must begin with a $ sign, and DTrace will automatically replace all the macro variables with the appropriate values when parsing your script.

Full list of macro variables can be found here, I will only talk about $target variable this time.

$target specifies the PID of the process you associate with your DTrace script.