IBM Support

Recommended Settings for Linux on System z Hosts running SLES11 SP2 or RHEL 6.3 releases

Preventive Service Planning


Abstract

SLES11 SP2 & RHEL6.3 have been tested on IBM System z hosts. The following describes the recommended multipath & udev settings.

Content

The following details the recommended multipath settings and udev rules for the attachment of zLinux hosts to SAN Volume Controller and Storwize V7000.

The settings are recommended to ensure path recovery in failover scenarios.

A host reboot is required after completing the following two steps.

1. Edit the multipath settings in /etc/multipath.conf
2. Edit the udev rules for SCSI command timeout


· Multipath settings

Edit /etc/multipath.conf with the following perameters.

For SLES11 SP2

1. dev_loss_tmo and fast_fail_tmo values (via /etc/multipath.conf)
defaults {
dev_loss_tmo 120
fast_io_fail_tmo 5
}

2. Controller settings (via /etc/multipath.conf)

devices{
device {
vendor "IBM"
product "2145"
path_grouping_policy group_by_prio
path_checker tur
features "1 queue_if_no_path"
prio alua
failback immediate
rr_min_io 1
}
}


For RHEL 6.3

devices{
device {
vendor "IBM"
product "2145"
path_grouping_policy group_by_prio
getuid_callout "/lib/udev/scsi_id --whitelisted --device=/dev/%n"
path_checker tur
checker tur
features "1 queue_if_no_path"
prio alua
failback immediate
rr_min_io 1
}
}

Confirm using multipathd -k"show config"


· Udev Rules

· Set the udev rules for SCSI command timeout
· Set SCSI command timeout to 120s. Refer to the following table.

OS Level Default Value for SCSI timeout Required Setting for SCSI timeout
RHEL 6.3 30 120
SLES 11 SP2 30 120


Create the following udev rule on the Linux host ( Applicable for RHEL 6.3 as well as SLES11 SP2 )

# cat /etc/udev/rules.d/99-ibm-2145.rules

# Set SCSI command timeout to 120s (default == 30 or 60) for IBM 2145 devices
SUBSYSTEM=="scsi", ACTION=="add", ATTR{vendor}=="IBM", ATTR{model}=="2145", ATTR{timeout}="120"

Cross reference information
Segment Product Component Platform Version Edition
Storage Virtualization SAN Volume Controller Not Applicable SAN Volume Controller 5.1, 6.1, 6.2, 6.3, 6.4
Disk Storage Systems IBM Storwize V7000 (2076) Not Applicable IBM Storwize V7000 6.1, 6.2, 6.3, 6.4
Disk Storage Systems IBM Storwize V7000 Unified (2073) Not Applicable Platform Independent 1.3, 1.4

Document information

More support for: IBM Storwize V7000 (2076)
6.4

Version: Version Independent

Operating system(s): Platform Independent

Reference #: S1004326

Modified date: 15 May 2013