We have an HA cluster of two servers, we're about to change the shared storage, we will be using a Dell MD3600f an FC storage array.
We have some problems configuring multipath.
We have found a Dell PDF document explaining how to configure the multipath to use scsi_dh_drac driver on CentOS 5.5.
At some point the documentation says :
Can someone please explain what does this mean?3 - Add DM-RDAC driver module parameter rdac_blacklist in /etc/modprobe.conf.local to support
RDAC/MPP coexistence.
Then is says :
4- Rebuild RAMdisk. Enable multipathd daemon using the command:
#chkconfig multipathd on
This command will enable multipathd during the boot up.
I did rebuild the initramfs but I did not add anything to it.
Now multipath -ll command shows this
[root@srv2 ~]# multipath -ll
olddata (3600c0ff000d5bb36dcf3f45101000000) dm-2 HP,MSA2012fc
[features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=1][active]
\_ 1:0:3:0 sde 8:64 [active][ready]
mpath5 (36f01faf000e25618000003ad5934ddfd) dm-1 DELL,MD36xxf
[features=3 queue_if_no_path pg_init_retries 50][hwhandler=1 rdac][rw]
\_ round-robin 0 [prio=100][enabled]
\_ 1:0:0:2 sdb 8:16 [active][ghost]
\_ round-robin 0 [prio=0][enabled]
\_ 1:0:1:2 sdd 8:48 [active][ready]
mpath4 (36f01faf000e25686000003f55934df9e) dm-0 DELL,MD36xxf
[features=3 queue_if_no_path pg_init_retries 50][hwhandler=1 rdac][rw]
\_ round-robin 0 [prio=100][enabled]
\_ 1:0:1:1 sdc 8:32 [active][ready]
\_ round-robin 0 [prio=0][enabled]
\_ 1:0:0:1 sda 8:0 [active][ghost]
In the Dell array, we have two paths, but I have one ready, the second is ghost, what does this means?
When we execute some commands like, lvs, vgs, sometimes the commands hang for a while before retuning the results.
Here is our mutlipath.conf file :
[root@srv2 ~]# cat /etc/multipath.conf
defaults {
udev_dir /dev
# polling_interval 10
# selector "round-robin 0"
# path_grouping_policy failover
# getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
# prio_callout "/bin/true"
# path_checker tur
# rr_min_io 100
# rr_weight uniform
# failback immediate
# no_path_retry 12
user_friendly_names yes
}
# The blacklist section - use this to blacklist a multipath device based on
# it's wwid ( using wwid ) or device names ( using devnode ) or
# vendor and product id ( using device block).
blacklist {
devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
devnode "^hd[a-z][[0-9]*]"
devnode "^raw[[0-9]*]"
devnode "^cciss!c[0-9]d[0-9]*"
device {
vendor "*"
product "Universal Xport"
}
}
multipaths {
multipath {
wwid 3600c0ff000d5bb36dcf3f45101000000
alias olddata
no_path_retry 10
}
}
# The devices section - used to define per storage array model settings
devices {
device {
vendor "HP"
product "MSA2[02]12fc|MSA2012i"
path_grouping_policy multibus
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
path_selector "round-robin 0"
rr_weight uniform
path_checker tur
hardware_handler "0"
failback immediate
no_path_retry 18
rr_min_io 100
}
device {
vendor "DELL"
product "MD36xxf"
path_grouping_policy group_by_prio
#prio rdac
#polling_interval 5
path_checker rdac
path_selector "round-robin 0"
hardware_handler "1 rdac"
failback immediate
features "2 pg_init_retries 50"
no_path_retry 30
rr_min_io 100
prio_callout "/sbin/mpath_prio_rdac /dev/%n"
}
}
as you can see the prio and polling_interval were taken from the Dell documentation, but were not recognized by the multlpath service.
Here is the link of the Dell documentation file, it's not a big : http://www.dell.com/downloads/global/pr ... ation.pdf
Thanks in advance
Regards