[CentOS] UC multipathd

Thu Feb 5 11:08:03 UTC 2015
Rushton Martin <JMRUSHTON at qinetiq.com>

>-----Original Message-----
>From: centos-bounces at centos.org [mailto:centos-bounces at centos.org] On
>Behalf Of Alexander Dalloz
>Sent: 04 February 2015 22:44
>To: CentOS mailing list
>Subject: Re: [CentOS] multipathd
>
>Am 04.02.2015 um 15:02 schrieb Rushton Martin:
>> Our cluster was supplied with two IBM DS3400 RAID arrays connected
>> with fibre channel.  Both are old and one is failing so we bought an
>> IBM
>> V3700 to replace it.  The V3700 complained that we were using the
>> IBM's RDAC driver (true) and we were advised to change to using Linux
>> multipath.  I've done that but the default configuration for the
>> DS3400s
>
>So you switched from IBM's proprietary multipath driver to the native
>Linux multipathing. Correct?

Yes.  We were told to do so by the suppliers of the V3700.

>
>> is:
>>          device {
>>                  vendor IBM
>>                  product 1726-4xx
>>                  path_checker rdac
>>                  features 1 queue_if_no_path
>>                  hardware_handler 1 rdac
>>                  prio_callout /sbin/mpath_prio_rdac /dev/%n
>>                  no_path_retry 300
>>                  rr_min_io 1000
>>          }
>
>The right settings are documented here:
>
>https://access.redhat.com/solutions/85223

Thanks, I shall investigate.  The stanza I've used was the one that multipath itself supplies.

>Yoi should be a little more specific about the conflict you see.

The V3700 GUI reports:

"Error 1624 : Controller configuration has unsupported RDAC mode"

Attempting to run the fix results in two messages:
----%<-------
Incorrect controller configuation
It is detected that storage system ds3400-01 has been incorrectly configured.
The storage system configuration has an unsupported RDAC mode.
----%<-------
Incorrect configuration

The storage system named ds3400-01 has been configured to use a failover mode called RDAC. This failover mode is not supported by the system, and will prevent the system from causing managed disks to fail over between controller A and controller B when required.
Resolve this by setting the host type in the storage system configuration as defined in the IBM® Storage ITE Software Configuration Guide.
If available, the correct host type will be "IBM TS SAN VCE".
Once the issue has been resolved, click Next to continue.
The following additional information may help with correcting the problem:
Storage system name: ds3400-01
WWNN (Worldwide Node Name): XX:XX:XX:XX:XX:XX:XX:XX
WWPN (Worldwide Port Number): XX:XX:XX:XX:XX:XX:XX:XX
Problem type : Unsupported RDAC Mode Set
----%<-------

The fix then runs, but reports the same 1624 error.

>
>> The V3700 is still complaining and I note the "path checker rdac" and
>> mpath_prio_rdac lines.  Is this rdac the same as IBM's RDAC, and if so
>> how can I get rid of it?
>
>The DS3400 is an OEM product, provided by NetApp. RDAC is the the name of
>the hardware access type originally for LSI Corp controllers, later on
>NetApp.
>
>mpath_prio_rdac is code from the Linux kernel.
>
>> OS is CentOS 5.3 (yes, I know - upgrade), filesystem is GPFS.
>
>Update! Not upgrade. That old piece of software is full of well known
>severe security issues and bugs already fixed. There is not really an
>excuse to not properly maintain a system.

Off-net machine.  Updates are non-trivial, download is over a slow broadband (between 500K and 1M) and takes well over 24 hours continuously.  Then I've still got to burn or copy to transfer.

>Alexander
>
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