Here is my config:

root@os-node1:~# uname  -a
Linux os-node1 3.16.0-48-generic #64~14.04.1-Ubuntu SMP Thu Aug 20
23:03:57 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux





root@os-node1:~# cat /etc/mdadm/mdadm.conf

DEVICE /dev/mapper/hgst-ssd*
CREATE owner=root group=disk mode=0660 auto=yes
HOMEHOST <system>
MAILADDR root
ARRAY /dev/md0 metadata=0.90 UUID=4472a74f:ca206897:3b82bcad:daeae9f9






root@os-node1:~# cat /etc/multipath.conf

blacklist {
       wwid 3600508b1001cbb0c5b5a2fe0a85e0053
       wwid 3600508b1001c33e8fe607dfd73043d03
       wwid 32020030102060804

}


multipaths {
       multipath {
               wwid                    35000cca04f1cbdfc
               alias                   hgst-ssd1
               path_grouping_policy    multibus
               path_selector           "round-robin 0"
               failback                2
               rr_weight               uniform
               no_path_retry           0
               rr_min_io               1000
       }

       multipath {
               wwid                    35000cca04f1cc050
               alias                   hgst-ssd2
               path_grouping_policy    multibus
               path_selector           "round-robin 0"
               failback                2
               rr_weight               uniform
               no_path_retry           0
               rr_min_io               1000
       }

       multipath {
               wwid                    35000cca04f1ce930
               alias                   hgst-ssd3
               path_grouping_policy    multibus
               path_selector           "round-robin 0"
               failback                2
               rr_weight               uniform
               no_path_retry           0
               rr_min_io               1000
       }

       multipath {
               wwid                    35000cca04f1ce1f4
               alias                   hgst-ssd4
               path_grouping_policy    multibus
               path_selector           "round-robin 0"
               failback                2
               rr_weight               uniform
               no_path_retry           0
               rr_min_io               1000
       }

       multipath {
               wwid                    35000cca04f1cbe18
               alias                   hgst-ssd5
               path_grouping_policy    multibus
               path_selector           "round-robin 0"
               failback                2
               rr_weight               uniform
               no_path_retry           0
               rr_min_io               1000
       }

       multipath {
               wwid                    35000cca04f1cdc58
               alias                   hgst-ssd6
               path_grouping_policy    multibus
               path_selector           "round-robin 0"
               failback                2
               rr_weight               uniform
               no_path_retry           0
               rr_min_io               1000



with this config I do:

root@os-node1:~# update-initramfs -u
update-initramfs: Generating /boot/initrd.img-3.16.0-48-generic


Then I reboot the computer but the mdadm raid doesn't start up. The
multipathed devides does start up:


root@os-node1:~# multipath -ll
Error: : Inappropriate ioctl for device
cciss TUR  failed in CCISS_GETLUNINFO: Inappropriate ioctl for device
Error: : Inappropriate ioctl for device
cciss TUR  failed in CCISS_GETLUNINFO: Inappropriate ioctl for device
hgst-ssd6 (35000cca04f1cdc58) dm-5 HGST    ,HUSMM1680ASS200
size=745G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 3:0:2:0 sde   8:64   active ready  running
  `- 4:0:2:0 sdk   8:160  active ready  running
hgst-ssd5 (35000cca04f1cbe18) dm-7 HGST    ,HUSMM1680ASS200
size=745G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 3:0:4:0 sdg   8:96   active ready  running
  `- 4:0:4:0 sdm   8:192  active ready  running
hgst-ssd4 (35000cca04f1ce1f4) dm-3 HGST    ,HUSMM1680ASS200
size=745G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 3:0:0:0 sdc   8:32   active ready  running
  `- 4:0:0:0 sdi   8:128  active ready  running
hgst-ssd3 (35000cca04f1ce930) dm-4 HGST    ,HUSMM1680ASS200
size=745G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 3:0:1:0 sdd   8:48   active ready  running
  `- 4:0:1:0 sdj   8:144  active ready  running
hgst-ssd2 (35000cca04f1cc050) dm-8 HGST    ,HUSMM1680ASS200
size=745G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 3:0:5:0 sdh   8:112  active ready  running
  `- 4:0:5:0 sdn   8:208  active ready  running
hgst-ssd1 (35000cca04f1cbdfc) dm-6 HGST    ,HUSMM1680ASS200
size=745G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 3:0:3:0 sdf   8:80   active ready  running
  `- 4:0:3:0 sdl   8:176  active ready  running


Regards,
Remek


On Fri, Dec 11, 2015 at 3:04 PM, Phil Turmel [off-list ref] wrote:

On 12/10/2015 05:44 PM, P. Remek wrote:

quoted

quoted

Order of device discovery is not guaranteed, but base devices will
almost always show up before multipath devices.  You have to filter out
the base devices from mdadm consideration:

Add a DEVICES statement to your mdadm.conf that only matches your
multipath device names, not the base names.  Then update your initramfs
so it applies to early boot as well.

This is something which I actually already tried. I specified in my
/etc/mdadm/mdadm.conf following:

DEVICE /dev/mapper/hgst-ssd*

In my /etc/multipath.conf I instruct dm-multipath to create
/dev/mapper/hgst-ssd1 /dev/mapper/hgst-ssd2 /dev/mapper/hgst-ssd3

You haven't said that you've updated your initramfs with this info.

quoted

But the only result is that after this config, the md raid is not
started at all. My conclusion was that when md raid was starting, the
multipath devices did not yet exist so it did not start up the array.

That would be an initramfs bug, most likely.  Modern initramfs like
dracut use incremental assembly to start arrays and subsystems as
devices are started, regardless what order they show up.

Phil