Booting from SAN on Multipath device HP P2000 storage

Hello.

I have managed to configure my storage HP 2000. I’m using three different disk types:

11 SAS disk 7200 rpm 1 TB size each
11 SAS disk 1500 rpm 600MB size each
11 SAS disk 1500 rpm 140MB size each

I want to use this storage for my virtual machines with KVM hypervisor

I have configured on Vdisk for each disk types. Each Vdisk group is RAID 5 with 1 hot spare and additionally I have one global spare just for safety.
Later I have created Volumes for my systems and configured Explicit mapping just for specific host.

Then I was able to install Centos 6 on this multipathd device choosing it from install menu:

Note that when I checked this multipath device and went Next to configure packages and then went back to select storage device there is no multipath device, only 4 identical scsi disks ( each one for each path) . But after restarting the installation wizard Multipath was again present.

Installation went fine, I was ready to boot from SAN but… My HP DL 380 couldn’t boot freshly installed system 😦

To make this work I had to change options in  HBA cards in my host to enable BIOS and boot. During host boot process I nedded to press Alt+Q to enter the menu:

And change Host adapter settings ( Host Adapter BIOS Enbled) for both of my cards:

Ok so my system could finally boot from SAN. Now the problem was that when I added any other Volumes from my storage they weren’t present as multipath device in my Centos. Every path to LUN was seen as single volume sda sdb sdc sdd.

To make this work I had to manually read the LUD uid using command

scsi_id -g -u /dev/xxx

And add this in my /etc/multipath.conf file:

blacklist_exceptions {
wwid “xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx”   # Lun

}

multipaths{

multipath{
alias mpathb
wwid “xxxxxxxxxxxxxxxxxxxxxxxx”
mode 0600
}
}

I don’t know what was the problem that my Centos 6 didn’t find this multipath right away, but this solution worked for me.

After reloading /etc/init.d/multipathd I was able to use multipath device /dev/multipathb

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