[dm-devel] multipath failover with 2x Emulex LP9802, setup, WWIDs

[Andreas Huck]

Hi,

I struggle to setup multipath devices by dmsetup, multipath-tools
and multipathd to get a pure failover path (no traffic sharing).
I followed the description at
http://christophe.varoqui.free.fr/multipath.html
and refered to all I could find on the web, but some questions
remain. Maybe you could give some advices?

This is the hardware:
Host: FSC RX300 (IA32)
HBA: 2 x Emulex LightPulse LP9802
Switch: 2 x Brocade 3800
Storage: S80, 2 x Mylex (only failover, no dual write allowed)


First, how to get a WWID?  I have 4 devices with 2 paths each.
`scsidev -s` should provide it but doesn't:

# scsidev -s
Serial number of /dev/scsi/sgh1-1c0i0l3: "0003cc7420000080e512cc740000000000000000"
Serial number of /dev/scsi/sdh1-0c0i0l3: "0003cc7420000080e512cc740000000000000000"
 HSV OS Id: 0
Serial number of /dev/scsi/sgh1-1c0i0l2: "0002cc7420000080e512cc740000000000000000"
Serial number of /dev/scsi/sdh1-0c0i0l2: "0002cc7420000080e512cc740000000000000000"
 HSV OS Id: 0
Serial number of /dev/scsi/sgh1-1c0i0l1: "0001cc7420000080e512cc740000000000000000"
Serial number of /dev/scsi/sdh1-0c0i0l1: "0001cc7420000080e512cc740000000000000000"
 HSV OS Id: 0
Serial number of /dev/scsi/sgh1-1c0i0l0: "0000cc7420000080e512cc740000000000000000"
Serial number of /dev/scsi/sdh1-0c0i0l0: "0000cc7420000080e512cc740000000000000000"
 HSV OS Id: 0
Serial number of /dev/scsi/sgh0-0c0i0l3: "0003cc7420000080e512cc740000000000000000"
Serial number of /dev/scsi/sdh0-0c0i0l3: "0003cc7420000080e512cc740000000000000000"
 HSV OS Id: 0
Serial number of /dev/scsi/sgh0-0c0i0l2: "0002cc7420000080e512cc740000000000000000"
Serial number of /dev/scsi/sdh0-0c0i0l2: "0002cc7420000080e512cc740000000000000000"
 HSV OS Id: 0
Serial number of /dev/scsi/sgh0-0c0i0l1: "0001cc7420000080e512cc740000000000000000"
Serial number of /dev/scsi/sdh0-0c0i0l1: "0001cc7420000080e512cc740000000000000000"
 HSV OS Id: 0
Serial number of /dev/scsi/sgh0-0c0i0l0: "0000cc7420000080e512cc740000000000000000"
Serial number of /dev/scsi/sdh0-0c0i0l0: "0000cc7420000080e512cc740000000000000000"
 HSV OS Id: 0


So do I need to provide WWIDs for /etc/multipath.conf ?
How to identify the devices if  for XXX=[a-h]:
# /sbin/scsi_id -g -p 0x83 -s /block/sdXXX
220000003390011d3
I.e. all IDs are equal (but configured right, i.e.
a=e,b=f,c=g,c=h).

Is it wise to take the unique path as ID? :
# ls -l /sys/block/sdb/device
/sys/block/sdb/device -> ../../devices/pci0000:04/0000:04:08.0/host0/0:0:0:1


The hardware is not listed in setup_default_hwtable and I wonder
whether I can define it by multipath.conf at all since sysfs does
provide the vendor but NOT the "product":

# ls  /sys/block/sdb/device/
.  ..  block  delete  detach_state  device_blocked  generic  model
online  power  queue_depth  rescan  rev  scsi_level  timeout  type  vendor

Instead I could use 'model "FC2502          "' - but that's not implemented.


I tried a direct approach by dmsetup, but didn't get a device:

# echo "0 274968576 multipath 10 2 1 round-robin 1 0 \
/dev/sdb 1 round-robin 1 0 /dev/sdf" | dmsetup create /dev/dm-0
k_set_name: Device /dev/dm-0 not found
Command failed

Maybe I am not too familiar with hotplug and udev.
I already did add a udev rule:
# grep dm /etc/udev/udev.rules
KERNEL="dm-[0-9]*", PROGRAM="/sbin/devmap_name %M %m", NAME="%k", SYMLINK="%c"

but

# /sbin/devmap_name 8 16
No devices found

Although the devices exist:
brw-rw----  1 root disk 8, 0 Jun 30 21:04 /dev/sda
brw-rw----  1 root disk 8, 16 Jun 30 21:04 /dev/sdb
brw-rw----  1 root disk 8, 32 Jun 30 21:04 /dev/sdc
brw-rw----  1 root disk 8, 48 Jun 30 21:04 /dev/sdd
brw-rw----  1 root disk 8, 64 Jun 30 21:04 /dev/sde
brw-rw----  1 root disk 8, 80 Jun 30 21:04 /dev/sdf
brw-rw----  1 root disk 8, 96 Jun 30 21:04 /dev/sdg
brw-rw----  1 root disk 8, 112 Jun 30 21:04 /dev/sdh


Does this look like some older bugs or do I overlook something
important here?

Last but not least, I use
kernel-smp-2.6.5-7.111
udev-021-36.32
multipath-tools-0.2.1-1.5
from SLES9 and also played around with
multipath-tools-0.3.7 from source.

So if you have some hints for me that would be great.
I would give some feedback and test results and in case of
success a small documentation as refund :-)


Thanks and kind regards,
Andreas