Devs,
We seem to having an issue with the time to failover over iSCSI.
The end goal here being to force a failover within 10 seconds to an
alternate path as defined by dm-multipath.
Distro: CentOS
Kernel version: 2.6.29.5
dm-multipath version: device-mapper-multipath-0.4.7-17.el5
iscsid version: iscsi-initiator-utils-6.2.0.868-0.7.el5
We have dm-multipath installed and configured with the following
configurations:
udev_dir /dev
polling_interval 3
selector "round-robin 0"
path_grouping_policy failover
getuid_callout "/sbin/scsi_id -g -u -
s /block/%n"
prio_callout /bin/true
path_checker readsector0
rr_min_io 10
max_fds
8192
rr_weight uniform
failback manual
no_path_retry fail
user_friendly_names yes
We have also modified scsi PDU timeout:
ACTION=="add", SUBSYSTEM=="scsi" , SYSFS{type}=="0|7|
14", \
RUN+="/bin/sh -c 'echo 5 > /sys$
$DEVPATH/timeout'"
in the /etc/udev/rules.d/50-udev.rules.
We have also modified some parameters in /etc/iscsi/iscsi.conf:
node.session.timeo.replacement_timeout = 5
node.conn[0].timeo.login_timeout = 5
node.conn[0].timeo.logout_timeout = 5
node.conn[0].timeo.noop_out_interval = 3
node.conn[0].timeo.noop_out_timeout = 1
Given the above configuration the failover takes place in 2 minutes.
Changing these values to lower or higher values doesn't seem to modify
the change failover time.
Any clues on how we can reduce this failover time would be
appreciated.
--
Akshay Lal
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