Luca, 

Here are the results the modifications you suggested :

# : mdadm -D /dev/md/0
/dev/md/0:
        Version : 00.90.00
  Creation Time : Tue Apr 23 15:55:33 2002
     Raid Level : multipath
     Array Size : 17688448 (16.86 GiB 18.11 GB)
   Raid Devices : 1
  Total Devices : 2
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Tue Apr 23 16:00:31 2002
          State : dirty, no-errors
 Active Devices : 1
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 1


    Number   Major   Minor   RaidDevice State
       0       8        1        0      active sync   
/dev/scsi/host2/bus0/target0/lun0/part1
       1      65       97        1      active   
/dev/scsi/host3/bus0/target0/lun0/part1
           UUID : b0191dc2:e89b155f:66c3e4e4:fa925d37

# : cat /proc/mdstat
md0 : active multipath scsi/host3/bus0/target0/lun0/part1[1] 
scsi/host2/bus0/target0/lun0/part1[0]
      17688448 blocks [1/2] [U]

Again only one HBA is utilized, which is verified via the previous testing I 
had run.  I believe that even after we hack the code to set all disks to 
'active', the raid code will still only use the first drive it finds that is 
not a spare.

--Snippit-- (multipath.c)
  * Mark all disks as spare to start with, then pick our
  * active disk.  If we have a disk that is marked active
  * in the sb, then use it, else use the first rdev.  
--Snippit--

Additionally I have noticed the following in my syslog on the mkraid of the 
multipath device.

--Snippit--
[events: 00000002]
[events: 00000002]
md: autorun ...
md: considering scsi/host3/bus0/target0/lun0/part1 ...
md:  adding scsi/host3/bus0/target0/lun0/part1 ...
md:  adding scsi/host2/bus0/target0/lun0/part1 ...
md: created md0
md: bind<scsi/host2/bus0/target0/lun0/part1,1>
md: bind<scsi/host3/bus0/target0/lun0/part1,2>
md: running: 
<scsi/host3/bus0/target0/lun0/part1><scsi/host2/bus0/target0/lun0/part1>
md: scsi/host3/bus0/target0/lun0/part1's event counter: 00000002
md: scsi/host2/bus0/target0/lun0/part1's event counter: 00000002
md0: max total readahead window set to 124k
md0: 1 data-disks, max readahead per data-disk: 124k
multipath: making IO path scsi/host3/bus0/target0/lun0/part1 a spare path 
(not in sync)
multipath: device scsi/host3/bus0/target0/lun0/part1 operational as IO path 1
multipath: device scsi/host2/bus0/target0/lun0/part1 operational as IO path 0
(checking disk 0)
(checking disk 1)
multipath: array md0 active with 1 out of 1 IO paths (1 spare IO paths)
md: updating md0 RAID superblock on device
md: (skipping alias scsi/host3/bus0/target0/lun0/part1 )
md: scsi/host2/bus0/target0/lun0/part1 [events: 00000003]<6>(write) 
scsi/host2/bus0/target0/lun0/part1's sb offset: 17688448

--Snippit--

Please note the comment about host3 being marked a spare path (not in sync).



Any comments as always, are welcome.


On April 19, 2002 05:58 pm, Luca Berra wrote:

Oops,
seems i forgot about spares :(

multipath.c sets all disks as spares to start with.
a dirty hack could be:

look for:
        /*
         * Mark all disks as spare to start with, then pick our
         * active disk.  If we have a disk that is marked active
         * in the sb, then use it, else use the first rdev.
         */

below you will find:
       if (disk_active(desc)) {
            if(!conf->working_disks) { //remove this line
                printk(OPERATIONAL, partition_name(rdev->dev),
                    desc->raid_disk);
                disk->operational = 1;
                disk->spare = 0;
                conf->working_disks++;
                def_rdev = rdev;
            } else { //remove this line
                mark_disk_spare(desc); //remove this line
            } //remove this line
        } else
            mark_disk_spare(desc);

remove the lines i market with //remove this line
and it should activate the disks

i wont have a system at hand to test this, so please let me know
if it works

we then need to clean up the logic for initialization
since is nonsense to set a disk as spare then reset it back
again as operational, but this could work for a start

good luck

L.