Multipathing with RHEL4 on BL25p to MSA1000

[Barry Lowe]

I have installed RHEL4 U3 on a BL25p connected to a MSA1000. I am looking for some advice on how best to configure my multipath.conf file and how to tell if it is working. Here's my latest attempt at a working conf file:

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 hp_sw
rr_min_io 100
rr_weight priorities
failback immediate
no_path_retry fail
user_friendly_name yes
}
devnode_blacklist {
wwid 26353900f02796769
devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
devnode "^hd[a-z]"
devnode "^cciss!c[0-9]d[0-9]*"
}
devices {
device {
vendor "COMPAQ "
product "MSA1000 "
path_grouping_policy failover
}
}

It's probably worth noting that the MSA1000 is in active/passive mode so only one path to it works at any time. The result of this at the moment means that my messages file gets clogged up with messages such as these:

Buffer I/O error on device sda, logical block 0
Device sda not ready.
end_request: I/O error, dev sda, sector 0

What advice can anyone give as to the correct settings to use in multipath.conf for this type of setup and should I expect to see so many errors being logged?

Thanks.

[Anthony Martin_1]

Hi Barry,
It looks like you need to put a partition on /dev/sda.
This will get rid of the messages.
Check the MSA100 to make sure the vendor id is COMPAQ. I think the firmware was updated to change from Compaq to HP at some stage.

Cheers
Anthony

[Serviceguard for Linux]

If you are using the QLogic HBA, then you should use QLogic mulitpath. If you use the HP supplied I believe multipath is neabled by default.

For device mapper check out - http://search.hp.com/redirect.html?type=REG&qt=emulex+linux+multipath+%22device+mapper%22&url=http%3A//h20000.www2.hp.com/bc/docs/support/SupportManual/c00635587/c00635587.pdf%3Fjumpid%3Dreg_R1002_USEN&pos=1

But be aware of the warning "This first release of Device Mapper is intended for use in limited environments. It is recommended to use with test environments and non-mission critical applications, to become familiar with the Device Mapper functionality. It is not recommended to use Device Mapper Multipath for your mission critical applications at this time, because caution should be exercised when implementing any new software into a production environment. Only features described in this document are supported with this release. Future releases will have increased functionality and usability."

[Barry Lowe]

Thanks for your reponses.

Anthony, sda shows up because it is in passive mode and sdb is the active path. Putting a partition on will make no difference as it can't be seen via that path. I'll check the vendor id though.

HP SfL, the document listed states:
"No Array Active-Passive support"
which I guess means it won't work? And if I can get it to work it won't be supported if it goes wrong.

My original question asked about whether or not it is valid to see such warnings as listed. I would expect the OS to realise that sda is not available.

[Serviceguard for Linux]

Barry,

On your comment of the OS realizing SDA is not available:

Because it is active/passive, the passive "side" shows up when the bus is scanned but cannot be used - therefore the error. I believe, since DM doesn't know about active/passive, it is checking periodically to see if a "bad" disk is repaired. This would make sense in an active/active environment.

Linux is still evolving.

[Barry Lowe]

Thanks. I guess I'll just have to ignore the error messages then.