RedHat 4.8 Smart Array p700m multipathing

[MikkoT]

I have installed RedHat 4.8 with kernel version 2.6.9-89.0.20.ELsmp to BL460cG6 with Smart Array P700m raid-controllers. Behind the raid controller is MSA2324sa raid array. System works fine with single path configuration to RAID array but multipathing configuration does not work.
I have compiled cpq_cciss-2.6.20-23 kernel module, because RedHat shipped module did not recognise the MSA2324sa raid array correctly.
hp_scsi_id command is also in use because standard scsi_id command does not recognise MSA2324sa raid array correctly.
hp_scsi_id reports the raid array like below:

hp_scsi_id -g -u -s /block/cciss\!c0d0
3600c0ff000da73d4dc94864b01000000

With this combination multipathing can be almost setup but it freezes on the on the stage of creating multipathing device, in kernel messages following messages are shown:
omcasg1 kernel: device-mapper: dm-multipath: unknown hardware handler type
omcasg1 kernel: device-mapper: error adding target to table
Is it so that RedHat 4.8 version device mapper (device-mapper-1.02.28-2.el4) would need to upgraded in order to get multipathing to work?

BR, MikkoT

[Steven E. Protter]

Shalom,

If you configure the smart array to present two disks as a raid 1 disk, the system only sees the one disk.

Multipathing does not come into play. This is actually a better way to go, because it takes part of i/o processing away from the CPU to a subsystem with a CPU.

SEP

[MikkoT]

Hi Mr. Protter,
thank you for your reply. I would like to rephrase my earlier message. I do not have local hard disk installed to the blade server. The MSA2324sa array is used for booting the blade. For redundancy purposes I would need at least two physical cable connection from C7000-chassis sas-switch pair to MSA2324sa array controllers. Therefore unfortunately RAID1 solution does not help me.
Does anyone has successfully implemented redundant connection with Smart Array p700m and MSA2324sa using RedHat 4 ES operating system?

BR, MikkoT

[D Block 2]

I'm think MSA is active-standby can you research making active-active within the MSA to the sas-switch? To confirm, can see any port links flashing when booting linux ? I assume the one side is only active. If this is the case being hardware msa config, then the software-kernel device-mapper will also see only one-side. I recall device-maper has a long-listing opiton to see all luns on all paths. if this sees only one side, then maybe again its the MSA end. Can you try to focus on the MSA and is it configured for active-active pathing.

[MikkoT]

Hi fellows,
thank you for your suggestions on this multipathing issue. MSA2324sa was already initially already configured as active-active so that wasn't a reason this time.

Finally after reading numerous discussions related to this kind of case on the web and testing different combinations a working solution was found.
The main problem with RedHat 4.8 is that the supplied cciss kernel module does not recognize p700m and MSA2324sa array. It was updated with open-source cciss driver, cpq_cciss-2.6.20-23.
Second thing is that standard scsi_id command does not support MSA2324sa array. HP has wrote their own hp_scsi_id tool that does support MSA2324sa. This can downloaded as a part HPDMmultipath-4.4.0 package. hp_scsi_id was utilized on multipath.conf instead of normal scsi_id.

In order to get multipath booting to work new initrd needs to complied with multipathing support and hp_scsi_id included in the initrd image.

Finally mount entries in the /etc/fstab are pointed to multipath devices.

With these modifications multipathing on RedHat 4.8 works like a charm.

[MikkoT]

See above report it contains a solution for multipathing problem with RedHat 4.8 and MSA2324sa.

BR, MikkoT