[dm-devel] multipath with SAS and FC.

[Roger Heflin]

You can use active/active on FC and on SAS.

But some cheaper/simpler arrays/devices are not active/active, they
are active/passive and that requires a scsi_dh* module to handle the
non-active/non-responding path correctly.  I don't know if yours is
one of those.

You will need to find the vendors how-to doc on the required config
options as some options will not work on some devices, and in some
cases there may need to also be things set in the array itself to
allow certain things multipath needs to do.

On Mon, Mar 1, 2021 at 7:54 AM <bchatelain at cines.fr> wrote:
>
> Hello,
>
> I try to use multipath with SAS disk, transported by Fiber Channel, on
> Dell Compellent.
> My volume is detected on 2x R440 PowerEdge hosted by Centos 8 and
> orchestrated by oVirt.
>
>
> Problematic :
>
> On my two ovirt node with the same configuration and hardware
> specifications,
> I give this same behavor, one of my two link, is flapping ACTIVE to FAILED
>
> Something like this :
> # multipath -ll
> 36000d31003d5c2000000000000000010 dm-3 COMPELNT,Compellent Vol
> size=1.5T features='1 queue_if_no_path' hwhandler='1 alua' wp=rw
> `-+- policy='service-time 0' prio=25 status=active
>    |- 1:0:0:2 sdb 8:16 active ready running
>    `- 1:0:1:2 sdc 8:32 failed ready running   -- looping failed/ready
>
>
> Some interesting stuff :
>
> # multipathd show config : Full @ https://pastebin.fr/85965
>
> blacklist {
> ···
>      device {
>          vendor "COMPELNT"
>          product "Compellent Vol"
>          path_grouping_policy "multibus"
>          no_path_retry "queue"
>      }
> ···
> }
>
>  LogZ : Full @ https://pastebin.fr/85968
> Feb 25 11:48:24 isildur-adm kernel: device-mapper: multipath: 253:3: Reinstating path 8:32.
> Feb 25 11:48:24 isildur-adm kernel: sd 1:0:1:2: alua: port group f01c state S non-preferred supports toluSNA
> Feb 25 11:48:24 isildur-adm kernel: device-mapper: multipath: 253:3: Failing path 8:32.
> Feb 25 11:48:25 isildur-adm multipathd[659460]: sdc: mark as failed
>
>
>  # lsscsi -l
> [0:2:0:0]    disk    DELL     PERC H330 Adp    4.30  /dev/sda
>    state=running queue_depth=256 scsi_level=6 type=0 device_blocked=0 timeout=90
> [1:0:0:2]    disk    COMPELNT Compellent Vol   0704  /dev/sdb
>    state=running queue_depth=254 scsi_level=6 type=0 device_blocked=0 timeout=30
> [1:0:1:2]    disk    COMPELNT Compellent Vol   0704  /dev/sdc
>    state=running queue_depth=254 scsi_level=6 type=0 device_blocked=0 timeout=30
>
>
>  # lsmod | grep fc
> bnx2fc                110592  0
> cnic                   69632  1 bnx2fc
> libfcoe                77824  2 qedf,bnx2fc
> libfc                 147456  3 qedf,bnx2fc,libfcoe
> scsi_transport_fc      69632  3 qedf,libfc,bnx2fc
>
>
>  # lsmod | grep sas
> mpt3sas  303104 4
> raid_class  16384 1 mpt3sas
> megaraid_sas  172032 2
> scsi_transport_sas  45056 1mpt3sas
>
>
>
> I've made a misconfiguration ?
> Is It possible to use SAS over FC ?
>
> Thank you.
>
>
> Regards,
> Benoit Chatelain.
>
>
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