[ovirt-users] multipath configuration for local disks?

[Matthias Leopold]

hi,

i'm using three different generations of hardware for my oVirt 
hypervisor hosts. they are not exactly the "same", but very "similar".

- all were installed with oVirt Node 4.1.x installers
- all have (2-4) local SSD disks for oVirt Node OS
- all were configured with manual partitioning and SW RAID 1 with two 
SSD disks for oVirt Node OS

after initializing the third generation of hosts (with 4 SSD disks) i 
noticed the difference in multipath configuration for the local disks. 
suddenly the two OS disks (for RAID 1) are not configured as multipath 
disks anymore, the unused other two are multipath disks. in the first 
two host generations the (only) two OS disks (for RAID 1) are configured 
as multipath disks.

after looking at this for the first time and briefly looking into 
multipath documentation i think that local disks shouldn't be included 
in multipath configuration at all. i tried to remove the local disks 
from multipathing (delete from wwids file, explicit blacklisting), to no 
avail.

i'm pasting two listings from the 4 SSD disk situation:

# lsscsi --scsi_id -g
[0:0:0:0]    disk    ATA      SAMSUNG MZ7LM480 204Q  /dev/sda   -  /dev/sg0
[0:0:1:0]    disk    ATA      SAMSUNG MZ7LM480 204Q  /dev/sdb   -  /dev/sg1
[0:0:2:0]    disk    ATA      SAMSUNG MZ7LM480 204Q  /dev/sdc 
SAMSUNG_MZ7LM480HMHQ-00005_S2UJNX0J102216  /dev/sg2
[0:0:3:0]    disk    ATA      SAMSUNG MZ7LM480 204Q  /dev/sdd 
SAMSUNG_MZ7LM480HMHQ-00005_S2UJNX0J102214  /dev/sg3

# ls -l /dev/disk/by-id/*SAMSUNG*
lrwxrwxrwx. 1 root root  9  9. Okt 12:07 
/dev/disk/by-id/ata-SAMSUNG_MZ7LM480HMHQ-00005_S2UJNX0J102212 -> ../../sdb
lrwxrwxrwx. 1 root root 10  9. Okt 12:07 
/dev/disk/by-id/ata-SAMSUNG_MZ7LM480HMHQ-00005_S2UJNX0J102212-part1 -> 
../../sdb1
lrwxrwxrwx. 1 root root 10  9. Okt 12:07 
/dev/disk/by-id/ata-SAMSUNG_MZ7LM480HMHQ-00005_S2UJNX0J102212-part2 -> 
../../sdb2
lrwxrwxrwx. 1 root root  9  9. Okt 12:07 
/dev/disk/by-id/ata-SAMSUNG_MZ7LM480HMHQ-00005_S2UJNX0J102214 -> ../../sdd
lrwxrwxrwx. 1 root root  9  9. Okt 12:07 
/dev/disk/by-id/ata-SAMSUNG_MZ7LM480HMHQ-00005_S2UJNX0J102216 -> ../../sdc
lrwxrwxrwx. 1 root root  9  9. Okt 12:07 
/dev/disk/by-id/ata-SAMSUNG_MZ7LM480HMHQ-00005_S2UJNX0J102222 -> ../../sda
lrwxrwxrwx. 1 root root 10  9. Okt 12:07 
/dev/disk/by-id/ata-SAMSUNG_MZ7LM480HMHQ-00005_S2UJNX0J102222-part1 -> 
../../sda1
lrwxrwxrwx. 1 root root 10  9. Okt 12:07 
/dev/disk/by-id/ata-SAMSUNG_MZ7LM480HMHQ-00005_S2UJNX0J102222-part2 -> 
../../sda2
lrwxrwxrwx. 1 root root 10  9. Okt 12:07 
/dev/disk/by-id/dm-name-SAMSUNG_MZ7LM480HMHQ-00005_S2UJNX0J102214 -> 
../../dm-6
lrwxrwxrwx. 1 root root 10  9. Okt 12:07 
/dev/disk/by-id/dm-name-SAMSUNG_MZ7LM480HMHQ-00005_S2UJNX0J102216 -> 
../../dm-5
lrwxrwxrwx. 1 root root 10  9. Okt 12:07 
/dev/disk/by-id/dm-uuid-mpath-SAMSUNG_MZ7LM480HMHQ-00005_S2UJNX0J102214 
-> ../../dm-6
lrwxrwxrwx. 1 root root 10  9. Okt 12:07 
/dev/disk/by-id/dm-uuid-mpath-SAMSUNG_MZ7LM480HMHQ-00005_S2UJNX0J102216 
-> ../../dm-5

can someone explain this behaviour? what is the _intended_ configuration?

thx
matthias