HP Mainframe Connectivity Design Guide

The Linux operating system has been running on zSeries and System z mainframes for more than
a decade. zLinux is available in two distributions—Red Hat and SUSE. Both are functionally
equivalent to each other from a channel and disk connectivity standpoint. zLinux can run as an
independent operating system on an LPAR or as a guest operating system under z/VM.
zLinux disk connectivity is unique in that it can use both mainframe ECKD volumes connected by
FICON (FC) CHPIDs and Open Systems SCSI logical units connected by Fibre Channel (FCP)
CHPIDs. Although zLinux can use FCP CHIPIDs extensively in either an LPAR or zVM guest
environment, it cannot use FCP exclusively. You must configure the zLinux boot device as FICON
because zSeries mainframes do not support IPL from an FCP device.
FICON CHPID connectivity for zLinux is exactly the same as for z/OS as discussed in “IBM zSeries
processor FICON support rules” (page 88). This section focuses on FCP CHPIDs and the support
of zLinux and FCP channels with HP P9500 storage.
zLinux can use CHPIDs configured in either of the following modes:
• FICON (FC) native mode—A typical FICON channel connected to a FICON CU.
◦ FICON CHPIDs use the IBM property FICON protocol as defined in the FC-SB-2, FC-SB-3,
or FC-SB-4 standards. For more information, see “FICON technology” (page 10).
◦ FICON CHPIDs, even if used for zLinux, are subject to all the FICON rules for connectivity
(such as, FICON ports only, single hop, and high integrity fabrics.)
• FCP mode—A channel on a FICON or FICON Express channel card that is connected to SCSI
storage controllers (primarily disk and tape) through a CU in a zLinux environment.
◦ FCP CHPIDs use the open systems SCSI-over-Fibre Channel protocol as defined in the
SCSI Fibre Channel Standards.
◦ FCP CHPIDs can be directly connected to the SCSI disk controller (z9 systems or later
only), or they can be connected to the controller via a SAN.
◦ The SAN, if used, is not subject to FICON-specific SAN rules. Instead, a SAN used for
FCP CHPIDs is subject to Fibre Channel SAN rules. This means that the fabric can have
multiple hops and does not need to meet the high integrity fabric rules (such as insistent
domain ID and fabric binding). However, a best practice for a mainframe environment
is that the SAN meet the high integrity rules regardless of the CHPID type.
◦ If FCP and FICON are mixed in the same fabric (intermix environment), the fabric is
required to meet the high integrity rules for FICON. FICON paths are limited to 1 hop,
and FCP paths through the fabric can have multiple hops.
NOTE: Each port on a channel card is a CHPID, and each CHPID can be configured as either
FC or FCP, but each CHPID can only be configured for one mode or the other.
92 Mainframe rules