Posts Tagged ‘disk devices’

Graphing on-demand Linux system performance parameters

Tuesday, May 20th, 2008

Current servers are way more powerful than we could have imagined before. With quad-core CPUs, even the simple dual-socket servers contain lots of horse-power. Remember our attitude towards CPU power five years ago, and see that we’re way beyond our needs.

When modern servers are equipped with at least eight cores, other, non-CPU related issues become noticeable. Storage, as always, remains a common bottleneck, and, as an increase in expectations always accommodate increase in abilities, memory and other elements can be the cause for performance degradation.

sar‘ is a known tool for Linux and other Unix flavors, however, understanding the contexts within is not trivial, and while the data is there, figuring what is relevant for the issue at hand becomes, with more disk devices, and more CPUs, even more complicated.

kSar is a simple java utility which makes this whole mess into a simple, readable graphs, capable of being exported to PDF for the pleasure of the customers (where applicable). It parses existing sar files, or the extracted contents of ‘sa’ files (from, by default, /var/log/sa/). It is a useful tool, and I recommend it with all my heart.

Alas, when it comes to parsing ‘sa’ files, you will need, in most cases, either to export the file into text on the source machine, or use a similar version of sysstat tools, as changes in versions reflect changes in the binary format used by sar.

You can obtain the sysstat utils from here, and compile it for your needs. You will need only ‘sar’ on your own machine.

An important note – you will not be able to compile sysstat utils using GCC 4.x. Only 3.x will do it. The error would look like:

warning: ‘packed’ attribute ignored for field of type `unsigned char…

followed by compilation errors. Using GCC version 3.x will work just fine.

HP-UX – allowed shells, and connecting FC Multipath to NetApp

Thursday, August 10th, 2006

When adding a certain shell to an HP-UX system, for example, /usr/bin/tcsh, each user set to use this shell will not be able to FTP to the machine, until there is entry in /etc/shells. The trick is that even if the file doesn’t exist, you have to create it. By default, HP-UX allows only /sbin/sh and /bin/sh shells, but as soon as you setup this file, you can allow more shells. Mind you that you have to include /sbin/sh and /bin/sh in /etc/shells, else other things might not work correctly. Taken from here.

Connecting HP-UX to SAN storage is never too simple. The actual list of actions is:

1. Install HP-UX drivers for the FC adapter

2. Map the PWWN obtained from (reading the sticker at the back of the machine, or querying the storage/SAN switch) the machine to the relevant LUNs.

3. Run “/usr/sbin/ioscan -fnC disk” and see that the new disk devices are detected.

4. Run “/usr/sbin/ioinit -i” to create the relevant device files.

A note – HP-UX might require a reboot after the initial connection. On several cases I’ve noticed that if the server was running for a while with disconnected fiber, only being connected during before startup would result in link and in SAN registration. Of course, the driver must be installed then.

If you are to connect your HP-UX to NetApp device, as we did, take a day (or more) notice and open “now” account in http://now.netapp.com. You can find documentation about HP-UX (including step-by-step), you can find the “SAN Attach Kit for HP-UX” which will make your life easier, and set of best-practice guides. Just follow these guides, and you will find it easy and simple task to do.