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Old 03-17-2009, 09:00 AM
Gianluca Cecchi
 
Default info on defaults and features key for 1750500

Hello,
I have an IBM DS6800 storage system that is identified as 1750500
[]# cat /proc/scsi/scsi
Attached devices:
...
Host: scsi1 Channel: 00 Id: 01 Lun: 00
Vendor: IBM Model: 1750500 Rev: .441
Type: Direct-Access ANSI SCSI revision: 05
...

My system is rh el 5U3 x86_64 and has two fc hba connected to two fc
switches (connected then to the 4 ports of the storage system).
sw version is device-mapper-multipath-0.4.7-23.el5

I have a doubt about default configuration.
In this moment:
in multipath.conf no particular setting about the storage model. I only have

defaults {
user_friendly_names yes
}

Under /usr/share/doc/device-mapper-multipath-0.4.7
multipath.conf.defaults says:
#defaults {
# udev_dir /dev
# polling_interval 5
# selector "round-robin 0"
# path_grouping_policy failover
# getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
# prio_callout none
# path_checker readsector0
# rr_min_io 1000
# rr_weight uniform
# failback manual
# no_path_retry fail
# user_friendly_names no
# bindings_file "/var/lib/multipath/bindings"
#}

and
# device {
# vendor "IBM"
# product "1750500"
# getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
# prio_callout "/sbin/mpath_prio_alua %d"
# features "1 queue_if_no_path"
# hardware_handler "0"
# path_grouping_policy group_by_prio
# failback immediate
# rr_weight uniform
# rr_min_io 1000
# path_checker tur
# }

multipath.conf.annotated says
# # name : no_path_retry
# # scope : multipath & multipathd
# # desc : tell the number of retries until disable queueing, or
# # "fail" means immediate failure (no queueing),
# # "queue" means never stop queueing
# # values : queue|fail|n (>0)
# # default : (null)
# #
# #no_path_retry queue


two questions:
1) what is the meaning of the line
features "1 queue_if_no_path"
? I didn't find anything about the "features" key.....
Is it the same as "no_path_retry=queue" ?

2) If the answer to 1) is no, taking for good the defaults above, does
this mean that in a default config I have on my system
no_path_retry fail
?

Is there a command where I can see the actual config ?
(if for example anyone wants to cross check defaults written in docs
and real code behaviour)

Thanks in advance,
Gianluca

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