Settings for Linux hosts
To ensure path recovery in failover scenarios, certain Device Mapper Multipath (DMMP) settings and udev rules for the attachment of Linux hosts to Storwize® V3700 are recommended. These settings are valid for IBM® System x®, all Intel or AMD-based servers, and Power® platforms.
- Editing the multipath settings in /etc/multipath.conf
- Editing the udev rules for SCSI command timeout
For each Linux distribution and releases within a distribution, refer to the default settings under [/usr/share/doc/device-mapper-multipath.*] for Red Hat and [/usr/share/doc/packages/multipath-tools] for Novell SuSE. Ensure that the entries added tomultipath.conf match the format and syntax for the required Linux distribution. Use the multipath.conf only from your related distribution and release. Do not copy the multipath.conf file from one distribution or release to another.
For some operating system levels, the "polling_interval" needs to be located under defaults instead of under device settings. If"polling_interval" is present in the device section, comment out "polling_interval" by using a # key.
Under Device Section
# polling_interval 30,
Under Defaults Section
defaults {
user_friendly_names yes
polling_interval 30
}
Multipath settings for specific Linux distributions and releases
Edit /etc/multipath.conf with the following parameters and confirm the changes by using ’multipathd -k"show config"’.
device {
vendor "IBM"
product "2145"
path_grouping_policy group_by_prio
getuid_callout "/lib/udev/scsi_id --whitelisted --device=/dev/%n"
features "1 queue_if_no_path"
prio alua
path_checker tur
failback immediate
no_path_retry "5"
rr_min_io_rq 1
# polling_interval 30
dev_loss_tmo 120
}
device {
vendor "IBM"
product "2145"
path_grouping_policy group_by_prio
features "1 queue_if_no_path"
path_checker "tur"
prio "alua"
failback "immediate"
no_path_retry "5"
rr_min_io "1"
# polling_interval 30
dev_loss_tmo 120
}
device {
vendor "IBM"
product "2145"
path_grouping_policy group_by_prio
prio alua
features "0"
no_path_retry 5
path_checker tur
rr_min_io 1
failback immediate
# polling_interval 30
dev_loss_tmo 120
}
device {
vendor "IBM"
product "2145"
path_grouping_policy "group_by_prio"
prio "alua"
path_checker "tur"
failback "immediate"
no_path_retry "5"
rr_min_io 1
dev_loss_tmo 120
}
Udev rules SCSI command timeout changes
Set the udev rules for SCSI command timeout.
Set SCSI command timeout to 120s.
Operating system level | Default | Required setting |
---|---|---|
RHEL62 | 30 | 120 |
SLES11SP1 | 60 | 120 |
SLES11SP2 | 30 | 120 |
Udev rules file creation
udev rules file
cat /etc/udev/rules.d/99-ibm-2145.rules
# Set SCSI command timeout to 120s (default == 30 or 60) for IBM 2145 devices
SUBSYSTEM=="block", ACTION=="add", ENV{ID_VENDOR}=="IBM",
ENV{ID_MODEL}=="2145", RUN+="/bin/sh -c 'echo 120 > /sys/block/%k/device/timeout'"
After you set up your volumes, locate the block device paths by running "multipath -ll | grep sd" from the command line, and repeatedly running "cat /sys/block/sdX/device/timeout" (where X is 2145 block device path), checking each for 120 seconds.
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