November 23, 2015

Red Hat Enterprise Linux (RHEL) 7.2 released

On November 19th 2015 Red Hat released the next regular update to their flag ship operating system.

The kernel level for 7.2 is kernel-3.10.0-327.el7. The number of technology previews for System z has been greatly reduced, successful testing allows now support for those features.

Here is my usual summary of links to more information:
From a Linux on z Systems perspective this is a major step. This is the first distribution that supports SMT2 natively.So if you install it, you will have twice as many logical CPUs.

(updated 11/23/2015) 

November 12, 2015

Fedora 23 for IBM z Systems released

The new Fedora 23 for z Systems / s390x was released 11/10/2015. Thanks to the Fedora team for making this available! The kernel level is kernel-4.2.3-300.

As usual the download is available from the Fedoraproject site and the respective mirrors and known issues  are covered in the wiki.

October 23, 2015

How long is a mainframe in service?

One of the really nice things about Linux on z is the fact that the underlying hardware has a long life. This means that for complex software solutions that need extensive and expensive testing you can keep the system going over a long time period. The Linux distributions on the mainframe are supporting this model with their long term support contracts.

But how long can you get service? There is a now updated summary presentation out on TechDocs called "IBM Mainframe Life Cycle History" (PPT, PDF). It has a nice overview chart which gives the answer to this question: the average support cycle over the past 21 years has been 11.3 years!

October 22, 2015

IBM Storage Support Matrix (SSIC) updated for Linux on z

This week there has been a major update on the  IBM System Storage Interoperation Center (SSIC). Now in addition to the high end boxes and Flash Systems also many entry and mid range boxes are supported like a V3500, V3700, V5000, V7000. To get a quick view select under connection "FCP (z Systems)":

So for all those systems no SVC is needed any more!

And as a side remark: all the supported tapes are also documented in the SSIC, 

October 12, 2015

Random number generators for Linux on z Systems

For Linux on z Systems there are multiple kernel interfaces to get to (pseudo) random data. First there are the two standard Linux interfaces.
  • /dev/random : blocking interface used for really good random numbers
  • /dev/urandom : nonblocking interface used for everything else
Those interfaces work the same on z Systems as they do on other platforms. However in highly virtualized environments there are really idle servers where nothing is happening. This means that there isn't a lot of entropy generated and therefore /dev/random will block.

On top for z Systems there are two additional interfaces:
  • /dev/prandom : this is a hardware assisted pseudo random number generator using the System z CPACF instructions. To enable it do a modprobe prng. Further details can be found in the "Device Drivers, Features, and Commands" book for upstream, SUSE and Red Hat. In those books search for prng. 
  • /dev/hwrng : this is a true random number generator using the CryptoExpress CCA co-processor function. For this to work, you need the hardware card installed and configured to your Linux. Then a modprobe z90crypt starts it. 
As expected prandom is faster than urandom. But the additional card with the real random number generator is even faster and doesn't use CPU. Obviously when you share the card the throughput will be split between the Linux images.

If your application is written against /dev/random and there isn't enouh entropy in the system, you can refill it by using the rngd daemon. To start it use then command rngd -r /dev/hwrng. Of course you need to install the rng-tools package first. Caveat: you may need to change the service configuration file to point to /dev/hwrng. Or you create the /dev/hwrandom (which is the default for rngd) device node by linking to /dev/hwrng.

September 21, 2015

KVM for IBM z Systems

After the announcement in August, KVM for IBM z Systems is now generally available.  This takes the open source approach for virtualization to the mainframe. 

Here are a few links for further details:
If you encounter any problems, please open a PMR with IBM. 

(updated 10/06/2015) 

September 14, 2015

The Virtualization Cookbook for IBM z Systems - updated

The Redbook "The Virtualization Cookbook for z/VM 6.3, RHEL 6.4 and SLES 11 SP3" and the corresponding code examples got an update to the latest distribution levels. They have also reorganized the material into three different books, which I personally don't like that much - but others say this is the way to go.

August 19, 2015

Minecraft on the Mainframe

LinuxCon video - Joran Siu

Joran Siu from the IBM Java team installed Minecraft Server on the mainframe. In this entertaining talk he shows the results and the optimizations used, some of them only available on zEC12 and z13.

August 18, 2015

Linux on System z - Financial Trading demo from LinuxCon

Donna Dillenberger is showing a pure open source demo on the mainframe combining all the new technologies like Spark, MongoDB, Postgres, MariaDB, Node.js, Docker, Chef etc.
It's using live analytics for streams from Twitter and S&P financial data, showing the power of realtime analysis on the mainframe.
She is also providing a look at the infrastrucure driving this and even shows a fail over from one site to another using Hyperswap.
Towards the end she is providing real performance data for some of the components used.
During this presentation your probably want to pause and playback to get all the information she packed into those 18 minutes. Here is a breakdown (minutes:seconds) for reference:
  • 0:00: demonstration
  • 7:48: a look at the infrastructure
  • 11:22: failover by killing one storage subsystem
  • 13:45: performance data
  • 17:00: agility & summary
(updated 8/19/2015)

August 17, 2015

LinuxCon announcements for Linux on z

Today IBM made some interesting announcements at LinuxCon. I'm going to cover more of the technical stuff in separate posts - this is for the overview.
(updated 9/23/2015)