![[Photo of the Author]](../../common/images2/CuneytGoksu.jpg)
by Cüneyt Göksu
<cuneytgoksu(at)usa.net>
About the author:
Database Specialist, working for more than 12 years with all
commercial databases on major platforms including Linux!
Content:
|
Linux for S/390 (IBM z-Series)
![[Illustration]](../../common/images2/article328/ibm390.gif)
Abstract:
S/390 is a robust hardware platform from IBM for large
enterprices. Linux is now running on it.
_________________ _________________ _________________
|
History
When the Linux Operating System first appeared on 1991, it's
been working on IBM PC Compatibles. Since then it has been
ported to many other architectures such as Apple, Atari and
68000 based Amiga computers, Sun Spark workstations; Alpha
based personal computers and MIPS, PowerPC, HP PA-RISC and ARM.
S/390 is the name of the mainframe type computer architecture
from IBM. This architecture has been used widely with IBM's VM,
VSE and z/OS (former MVS and OS/390) operating systems. IBM has
chosen Linux, as one of the "Native" Operating System for this
solid architecture since 1999.
The most important reason to implement Linux, on the S/390
platform was to consolidat the connectivity among Legacy
Applications, Linux Applications and Middleware applications
such as web server, mail server, application server, firewall
etc.
It is widely said that, Linux works as an API or emulation on
the S/390 platform but it is not true, it works as a "native"
operating system so that all the hardware capability of this
platform is used. Linux Kernel and Common Code are used without
any modification and the Linux system structure remains
untouched. Only some "adaptations" are required to match and
implement S/390 architecture specifics. It works with the ASCII
character set instead of EBCIDIC.
Linux Integration to s/390 and the zSeries Achitecture
Linux can be installed in three different ways on a S/390
platform.
- Native Mode: It is installed directly on the
system hardware, more likely not a preferred solution,
because only one operating system runs on the hardware
level.
- Logical Partitions (LPAR): With Hardware
partitioning enabling up to 15 "Logical Partitions" each of
which runs a separate operating system, traditional ones such
as (MVS, VSE, OS/390) and Linux.
- Virtual Partitions (z/VM): This is called z/Series
virtualization technology. It supports for large numbers of
Linux images (1000+) with rich system management capabilities
on the same hardware. This way of installation is very
flexible and great for server systems.
In the following diagram those three types of installations are
shown:
If the required number of Linux servers is 15 or less,
then the LPAR solution is a good choice. If you need more, 100 or 1000
Linux Images, z/VM will be the answer.
Red Hat, SuSE and Turbolinux are major distributors for S/390
and zSeries.
You can use the links below to download them.
Red Hat:
SuSE:
TurboLinux:
There are also some distributions in binary. You can get
them from the links below.
Distributions for s/390 and zSeries
The Requirements for running Linux on the S/390
- 9672 G5/G6, Multirise 3000 or z/Series 800, 900, 990 IBM
Processor
- 64Mb+ Memory (very minimum - distributions and
applications dependent)
- 500 Cyl + Disk space ( Model 3390 - small minimum
system)
- IBM Network Device Support (one required) Ethe
- rnet, Token Ring, Fast Ethernet, ESCON, OSA or
HiperSocket. There are more devices to support.
- Before Linux can use a device the associated driver for
zSeries and S/390 device must be available to the
kernel.
- There are kernel resident drivers and external drivers
for S/390 and zSeries devices.
- External drivers are modules loaded on request with their
parameters by means of commands.
- Resident drivers receive their parameters at boot time,
from a kernel parameter line, held in a file.
- Non open source, OCO (Object Code Only), drivers are
drivers subject to license conditions (i.e. QETH for OSA
Express GbE and Hipersocket, Tape 3590) OCO drivers may not
be provided with all distribution and need to be downloaded
from IBM Developer Works when not part of the distribution
Why Linux for s/390 ?
The most important reason is server consolidation.
The three-tiered application architecture can be easily done
in two-tiered hardware. (Client / Application Server / Data
Server) these 3 classic steps can be joined in the S/390 like
(Application Servers / Databases). Hipersocket and Fiberchannel
features support the communication subsystem features and
connection problems disappear. Legacy Applications became
Distributed Applications then web based applications.
First, data then applications are distributed everywhere. The
number of servers increased enormously. This increase brought
some problems:
- Each and every new server means, new hardware, space,
capacity increase in cooling, cabling, connection etc. So
every time those
"physical" parameters
have to be monitored and adjusted.
- All software has to be licensed in each server which
means additional cost. For instance, your database
has to be licensed on each server on a per CPU bases.
- Connectivity is another important issue. Cabling,
gateways, switches, routers, all those components increase
the total cost.
- Disaster Recovery (DR) Solution is almost impossible with
individual servers. Operation and Maintenance costs of DR
gets higher, more complicated and impossible with the huge
number of servers.
- Database / Application / System Management issues, CPU
and Workload Sharing have to be done individually, for
each and every server.
Those were some of the potential problems in case Linux
images are run on different hardware. If all of them are run on
a single S/390 platform then the situation changes:
- Although all Linux Images share the same hardware (CPU,
I/O Subsystem, Memory, etc...) they
behave like individual, mutually exclusive, logical servers
and can be used for different purpose applications. In this
way, the increase of the number of servers does not affect
the maintenance costs. It can be monitored and controlled
easily and saves time. While sharing the resources
the throughput of the system is maximized.
- All servers share the same CPU, so that software license
fees decrease.
- All the connections among servers are internal, so that,
communication overhead because of hardware is almost nothing
and network performance is maximized.
- Adding a new server is just easy as cloning of a logical
server.
- Disaster Recovery is much more easy, realistic and
feasible. DASD (Direct Access Storage Device) Farms and Subsystem can quickly and
safely be copied in minutes with FlashCopy, PPRC
(Peer-To-Peer-Remote-Copy) or Snapshot features.
Resources:
- Linux for S/390, IBM Redbook
- Linux for z/Series, Atruro Calandrino, zSeries Tech.
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