Akshay Lal wrote:
Mike Snitzer wrote:
On Fri, Aug 07 2009 at 5:07pm -0400,
Akshay Lal <alal@xxxxxxxxxxxxxx> wrote:
Mike Snitzer wrote:
On Fri, Aug 07 2009 at 4:25pm -0400,
Akshay Lal <alal@xxxxxxxxxxxxxx> wrote:
I'm having a few issues with path priorities. It seems that the
choice of path to use during I/O is independent of the user
defined priorities for each path.
I am setting the priorities by executing writing a script that is
used by prio_callout. This seems to work when I execute multipath
-ll since all the specified priorities show up correctly. (the
path_grouping_policy being used is failover)
...
Is there something I'm doing wrong? I would like to be able to
define the priorities per device, and ensure that data only
traverses on the lower priority path when
a) a failure to the first path (path with a higher priority) occures
b) no other path with a higher priority exists
Do things behave as you'd like if you change path_grouping_policy to
'group_by_prio'?
Mike
Mike:
It seems that if I were to set the path_grouping_policy to
"group_by_prio", then it seems to be working similar to a multibus
configuration. What I would like is for within a single multipath
group, (say mpath1), specify a primary path and an
alternate/failover path. If I can make this configurable via user
land tool that'd be great. In this vein, I had considered
priorities with hope that if I can set the priority of a certain
path within a group then the path with the highest priority will
always be chosen and the other path (with the lower priority) will
only come into play when the primary goes down.
Below is the output of the multipath -ll & conf file when setting
the path_grouping_policy to group_by_prio.
multipath -ll:
--------------
mpath2 (244534e3833623961) dm-1 DSNET,Dispersed Store
[size=47G][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=15][enabled]
\_ 85:0:0:0 sdc 8:32 [active][ready]
\_ 87:0:0:0 sde 8:64 [active][ready]
mpath1 (244534e3266616134) dm-0 DSNET,Dispersed Store
[size=47G][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=15][active]
\_ 84:0:0:0 sdb 8:16 [active][ready]
\_ 86:0:0:0 sdd 8:48 [active][ready]
/etc/multipath.conf:
--------------------
defaults {
udev_dir /dev
polling_interval 1
selector "round-robin 0"
path_grouping_policy group_by_prio
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
prio_callout "/bin/bash
/root/MultipathScripts/mpath_prio_alt %n"
path_checker tur
rr_min_io 128
max_fds 8192
rr_weight priorities
failback immediate
no_path_retry queue
user_friendly_names yes
}
Please don't top-post.
I'm pretty sure John meant to say "group_by_prio" rather than "failover"
in his initial reply to this thread. John originally got this insight
(dummy device section et. al. applies to RHEL 5.3) back in April:
https://www.redhat.com/archives/dm-devel/2009-April/msg00157.html
Which multipath/distro are you using?
Mike
I tried out John's approach as well and it still seems to be giving me
the similar results to what I mentioned before, i.e., replicating
multibus
Priority list:
--------------
192.168.7.103:3260-iscsi-iqn.2008-07.com.cleversafe:vault-2 5
192.168.7.106:3260-iscsi-iqn.2008-07.com.cleversafe:vault-2 10
192.168.7.103:3260-iscsi-iqn.2008-07.com.cleversafe:vault-1 10
192.168.7.106:3260-iscsi-iqn.2008-07.com.cleversafe:vault-1 5
iSCSI disk associated with iSCSI sessions:
------------------------------------------
Target: iqn.2008-07.com.cleversafe:vault-1
Current Portal: 192.168.7.106:3260,1
Persistent Portal: 192.168.7.106:3260,1
Attached scsi disk sdb State: running
Current Portal: 192.168.7.103:3260,1
Persistent Portal: 192.168.7.103:3260,1
Attached scsi disk sdd State: running
Target: iqn.2008-07.com.cleversafe:vault-2
Current Portal: 192.168.7.106:3260,1
Persistent Portal: 192.168.7.106:3260,1
Attached scsi disk sdc State: running
Current Portal: 192.168.7.103:3260,1
Persistent Portal: 192.168.7.103:3260,1
Attached scsi disk sde State: running
multipath -ll:
---------------
mpath2 (244534e3833623961) dm-1 DSNET,Dispersed Store
[size=47G][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=15][enabled]
\_ 85:0:0:0 sdc 8:32 [active][ready]
\_ 87:0:0:0 sde 8:64 [active][ready]
mpath1 (244534e3266616134) dm-0 DSNET,Dispersed Store
[size=47G][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=15][enabled]
\_ 84:0:0:0 sdb 8:16 [active][ready]
\_ 86:0:0:0 sdd 8:48 [active][ready]
Versions being used:
dm-multipath: device-mapper-multipath-0.4.7-23.el5_3.4
kernel: 2.6.29.6
Sorry I forgot to add the multipath conf file
/etc/multipath.conf :
---------------------
# Blacklist all devices by default. Remove this to enable multipathing
# on the default devices.
#blacklist {
# devnode "*"
#}
##
## Defaults for the multipath daemon
##
#
defaults {
udev_dir /dev
polling_interval 1
selector "round-robin 0"
path_grouping_policy group_by_prio
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
prio_callout "/bin/bash /sbin/mpath_prio_alt %n"
path_checker tur
# rr_min_io 128
max_fds 8192
rr_weight uniform
failback immediate
no_path_retry queue
user_friendly_names yes
}
devices {
device {
vendor "dummy"
product "dummy"
prio_callout "/sbin/mpath_prio_alt %n"
}
}
--
Akshay Lal
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