[CentOS] HBA enumeration and multipath configuration

[Tom Robinson]

Sorry, I'm posting this question again as my original post go abducted by a different thread due to
stupid way I replied to that thread and changed the subject as a new post. My apologies if there's
any confusion.

On 14/04/15 10:05, Tom Robinson wrote:
> # cat /etc/redhat-release
> CentOS Linux release 7.1.1503 (Core)
> # uname -r
> 3.10.0-123.20.1.el7.x86_64
>
> Hi,
>
> We use iSCSI over a 10G Ethernet Adapter and SRP over an Infiniband adapter to provide multipathing
> to our storage:
>
> # lspci | grep 10-Gigabit
> 81:00.0 Ethernet controller: Intel Corporation 82599ES 10-Gigabit SFI/SFP+ Network Connection (rev 01)
> 81:00.1 Ethernet controller: Intel Corporation 82599ES 10-Gigabit SFI/SFP+ Network Connection (rev 01)
> # lspci | grep Mellanox
> 06:00.0 InfiniBand: Mellanox Technologies MT26428 [ConnectX VPI PCIe 2.0 5GT/s - IB QDR / 10GigE]
> (rev b0)
>
> Originally the HBAs came up as host0, host1 and host2. After recent reboots we get host1, host2 and
> host3:
>
> # ls -l /sys/class/scsi_host/host*
> lrwxrwxrwx. 1 root root 0 Apr  9 19:10 /sys/class/scsi_host/host1 ->
> ../../devices/platform/host1/scsi_host/host1
> lrwxrwxrwx. 1 root root 0 Apr  9 08:12 /sys/class/scsi_host/host2 ->
> ../../devices/pci0000:00/0000:00:03.2/0000:06:00.0/host2/scsi_host/host2
> lrwxrwxrwx. 1 root root 0 Apr  9 08:12 /sys/class/scsi_host/host3 ->
> ../../devices/pci0000:00/0000:00:03.2/0000:06:00.0/host3/scsi_host/host3
>
> I've observed that at different times during configuration of this host we have had varying
> combinations of the mapping of HBA to an enumerated /sys node. e.g.:
>
> host0
> host2
> host3
>
> or
>
> host1
> host3
> host4
>
> other combinations, etc.
>
> This messes up our multipath filtering for weightedpath priority settings. From /etc/multipath.conf:
>
> defaults {
>         user_friendly_names no
>         find_multipaths yes
>         prio weightedpath
>         prio_args "hbtl 0:.:.:.* 1 [1-9]:.:.:.* 10"
>         path_grouping_policy group_by_prio
>         path_selector "service-time 0"
>         failback immediate
>         polling_interval 5
>         no_path_retry 12
> }
>
> The setting for prio_args fails to set the correct path map topology and priority against an HBA as
> I can't predict what HBA is what. Consistently iSCSI claims the lowest number but I can't say if
> that's going to be 0 or 1 a this stage.
>
> Does anyone know how to configure HBAs to stay on a fixed enumeration at boot?
>
> Kind regards,
> Tom
>
>
>
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