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

[christophe varoqui]

Le jeudi 25 novembre 2004 à 08:55 +0100, Andreas Huck a écrit :
> Hi,
> 
> I struggle to setup multipath devices by dmsetup, multipath-tools
> and multipathd. 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?
> 
I'd rather remove this doc as it out of date and generate more trouble
than enlightenment.

> First, how to get a WWID?  I have 4 devices with 2 paths each.
> `scsidev -s` should provide it but doesn't:
> 
what is the output of "multipath -v2" ?

> 
> So how can I provide WWIDs for /etc/multipath.conf ?
> 
That is only necessary for aliases.
You can safely leave the config file multipath section empty.

> How to identify the devices if  for XXX=[a-h]:
> # /sbin/scsi_id -g -p 0x83 -s /block/sdXXX
> 220000003390011d3
>
And without "-p 0x83" ?

> I.e. all IDs are equal (but configured right, i.e.
> a=e,b=f,c=g,d=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
> 
No : we want a unique LU id, not a unique path id.

> 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":
> 
Sane defaults are applied when there is no corresponding entry in the
config file nor in setup_default_hwtable. Notably the failover pgpolicy
is selected, which is what you want.

> # 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.
> 
This is just terminology : "vendor / product /rev" used by most scsi
people, "vendor / model / rev" chosen by dreaming sysfs developers :)

model == product, so you can add the configlet if you want.

> 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
> 
# echo "0 274968576 multipath 10 2 1 round-robin 1 0 \
/dev/sdb 1 round-robin 1 0 /dev/sdf" | dmsetup create
just_the_map_name_you_want_not_a_path

> 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
> 
major:minor are devmap's one, as listed in "dmsetup ls" ?
And the map must exist for the command to work.

> 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
> 
> Do I overlook something important here?
> 
certainly :)

> Last but not least, I use
> kernel-smp-2.6.5-7.111
> udev-021-36.32
> multipath-tools-0.2.1-1.5
> device-mapper-1.00.09-17.5
> from SLES9 and also played around with multipath-tools-0.3.7 from source.
> 
I guess you'll have more feedback from Suse folk then.
I don't really know how the combination in SLES9 behave and what patch
pile they applied to the listed products.

> So if you have some hints for me that would be great.
> 
Hope it is enough to get you a bit further.

regards,
-- 
christophe varoqui <christophe.varoqui at free.fr>