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Operating System/400 (5722-SS1)
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iSeries Handbook
as an integrated core business solution. Linux inherits important strengths and reliability
features of the iSeries architecture.
OS/400 is enhanced to support Linux running in a secondary logical partition. The primary
partition must run OS/400 V5R1 and can support up to 31 Linux partitions, depending on the
iSeries model.
Selected new processor features for iSeries Model 270, 820, and 840 servers, allow Linux to
run in a shared processor pool, where one processor can be shared between four OS/400
and Linux partitions.
The iSeries Logical Partition capability (LPAR) gives you the flexibility to move processor and
memory resources between Linux partitions. This movement requires a restart of the affected
Linux partitions. On existing n-way processor features for iSeries Model 820, 830 and 840
servers, Linux requires a minimum of one processor per Linux environment.
The Linux environment on iSeries supports two types of I/O: virtual and direct. A Linux server
in a partition can take advantage of both virtual and direct I/O. A Linux partition can use the
Virtual LAN capability to establish multiple high-speed TCP/IP connections between logical
partitions without additional communication hardware.
With Virtual I/O, the I/O resources (disk, tape, CD-ROM) are owned by an OS/400 partition.
OS/400 shares the resources with Linux. The partition sharing the resources is called the
host. The host does not have to be the primary partition.
One partition can be the host for multiple Linux partitions. The shared resources are under
OS/400 management. For example, disk space is allocated from OS/400's disk drives for
Linux to use.
OS/400 provides the RAID protection and some backup/restore facilities for the Linux
environment. Virtual I/O takes advantage of the technology used with the Integrated xSeries
Server. The Network Server Description has been enhanced to support Linux in a similar way.
For example, Linux is started with a vary on command of the NWSD and stopped with a vary
off command.
The Virtual I/O devices supported include disk, tape, CD-ROM and DVD. With disk, space
owned by OS/400 is reserved for Linux. iSeries disk and removable media devices can be
configured for Linux partitions using the OS/400 Network Server Description (NWSD)
commands to provide a simple, flexible, and integrated storage solution.
With Direct I/O, the devices are owned by Linux. OS/400 does not see the devices and can
not directly use them. Specific iSeries I/O adapters are supported in Direct I/O environment.
Specific Ultra SCSI 2 Adapters for Disk, Tape, CD-ROM, and DVD connections are
supported. In addition the iSeries 1 Gb Ethernet adapter, the 10/100 Mb Ethernet adapter,
and the token-ring adapter are also supported. Since Linux does not support IOPs, they are