Attaching both MSA2060 channels to HBA results in double the OS discovered SCSI devices

[sdrake48]

Configuring single DL385 Gen11 installation using MSA2060 vi e208e-p as storage.  I have two volumes, both in Pool A. I create the Host with 2 initiators and cable both Channel A and B to the e208e-p.  I can install and boot a 2 logical drive configuration of SLES15 SP5. Partitioner shows that 4 SCSI devices are detected (/dev/sda, /dev/sdb, /dev/sdc, /dev/sdd).  sdc and sdd should not be present.  If I remove cable from e208e-p to Channel B and reboot the OS, 2 scsi devices are detected (as hoped); /dev/sda and /dev/sdb.  Also, quick read performance test (hdparm -t /dev/sda) yields half the read performance when both Channels attached as compared to one channel attached.  Any ideas?

[sdrake48]

The only reason I am using a SAN instead of a disk enclosure is that the Gen11 does not support attachment to D3710 external enclosure with any RAID controller that has cache.  Only e208e-p (no cache) is supported.  Performance is inadequate without write cache.  Only option I can find is MSA attached via e208e-p used in HBA mode, utilizing the cache in the MSA.  

[JonPaul · Accepted solution]

@sdrake48 
It would be strongy recommended to install Device Mapper multipath to your system.  This will combine the /dev/sd_  into a single /dev/mapper/_____  device and allow you to have automatic failover. The default Multipath rules will work but here are the optimized configuration options:
Path Management Notes
Add to /etc/multipath.conf devices section:
device {
vendor "HPE"
product "MSA [12]060 SAS"
path_grouping_policy "group_by_prio"
prio "alua"
path_selector "round-robin 0"
failback "immediate"
no_path_retry 18
}

Are you presenting 2 Volumes to the system?  That is the only way I can think of that you have multiple devices disappear when you remove a single cable.

[sdrake48]

Thank you.  Multipath looks promising. Will investigate implementing via autoyast during installation. 

[sdrake48]

Yes to multiple logical drives. I have 3 configurations to test; 1, 2, and 3 logical drives. In this particular example I have installed on 2 logical drives.

[sdrake48]

Multipath solved this issue.  Unfortunately, our single linux server Disaster Recovery solution does not support multipath....so is not an option for us.  In our case, a single connection from server to MSA2060 will be used.

[Sunitha_Mod]

Hello @sdrake48,

Great!

We are glad to know the problem has been resolved.