[ovirt-users] multipath configuration for local disks?

[Yaniv Kaul]

On Oct 10, 2017 12:23 PM, "Matthias Leopold" <
matthias.leopold at meduniwien.ac.at> wrote:

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.


I may be wrong but it rarely matters on local disks. Unless they have some
kind of active-active (multi-channel?) controllers.
Y.

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_MZ
7LM480HMHQ-00005_S2UJNX0J102212 -> ../../sdb
lrwxrwxrwx. 1 root root 10  9. Okt 12:07 /dev/disk/by-id/ata-SAMSUNG_MZ
7LM480HMHQ-00005_S2UJNX0J102212-part1 -> ../../sdb1
lrwxrwxrwx. 1 root root 10  9. Okt 12:07 /dev/disk/by-id/ata-SAMSUNG_MZ
7LM480HMHQ-00005_S2UJNX0J102212-part2 -> ../../sdb2
lrwxrwxrwx. 1 root root  9  9. Okt 12:07 /dev/disk/by-id/ata-SAMSUNG_MZ
7LM480HMHQ-00005_S2UJNX0J102214 -> ../../sdd
lrwxrwxrwx. 1 root root  9  9. Okt 12:07 /dev/disk/by-id/ata-SAMSUNG_MZ
7LM480HMHQ-00005_S2UJNX0J102216 -> ../../sdc
lrwxrwxrwx. 1 root root  9  9. Okt 12:07 /dev/disk/by-id/ata-SAMSUNG_MZ
7LM480HMHQ-00005_S2UJNX0J102222 -> ../../sda
lrwxrwxrwx. 1 root root 10  9. Okt 12:07 /dev/disk/by-id/ata-SAMSUNG_MZ
7LM480HMHQ-00005_S2UJNX0J102222-part1 -> ../../sda1
lrwxrwxrwx. 1 root root 10  9. Okt 12:07 /dev/disk/by-id/ata-SAMSUNG_MZ
7LM480HMHQ-00005_S2UJNX0J102222-part2 -> ../../sda2
lrwxrwxrwx. 1 root root 10  9. Okt 12:07 /dev/disk/by-id/dm-name-SAMSUN
G_MZ7LM480HMHQ-00005_S2UJNX0J102214 -> ../../dm-6
lrwxrwxrwx. 1 root root 10  9. Okt 12:07 /dev/disk/by-id/dm-name-SAMSUN
G_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



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