multipath -ll output discrepancy for IBM 1818 on SLES 11 SP1....

multipath -ll output discrepancy for IBM 1818 on SLES 11 SP1....

[Dharmesh Kamdar]

Hi,

We have a SLES 11 SP1 running with following snippet in multpath.conf

##########################
    device {
                vendor "IBM"
                product "1818"
                path_grouping_policy group_by_prio
                prio rdac
                getuid_callout "/lib/udev/scsi_id -g -u -d /dev/%n"
                polling_interval 5
                path_checker rdac
                path_selector "round-robin 0"
                hardware_handler "1 rdac"
                failback immediate
                features "2 pg_init_retries 50"
                no_path_retry 30
                rr_min_io 100
        }
#################################

But when we see "multipath -ll" output we see:
mpathca (3600a0b8000475c52000006a04b60f1d9) dm-38 IBM,1818      FAStT
size=2.0G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 rdac' 
wp=rw
|-+- policy='round-robin 0' prio=6 status=active
| |- 4:0:5:1  sdcz 70:112 active ready running
| `- 5:0:5:1  sddl 71:48  active ready running
`-+- policy='round-robin 0' prio=1 status=enabled
  |- 4:0:4:1  sdcx 70:80  active ghost running
  `- 5:0:3:1  sddh 70:240 active ghost running


So, my question is : even if we mention 
                             features "2 pg_init_retries 50" 

why are we seeing " features='3 queue_if_no_path pg_init_retries 50' 
hwhandler='1 rdac' wp=rw" in the multipath -ll output ?

1) Where is this "3" coming from  ? and what is it's significance ?? 

2) Is this "3" next to the features in "multipath -ll" output as expected (even 
though we mention "2 pg_init_retries 50" ) in our multipath.conf ??

(We've rebooted and regenerated multipath maps multiple times by "multipath -F" 
and then "multipath" )....but we still see this "discrepancy" (of "2" vs "3") ?

Will appreciate if someone can explain us.

Thanks,
Dharmesh.

Re: multipath -ll output discrepancy for IBM 1818 on SLES 11 SP1....

[Bryn M. Reeves]

On 04/01/2011 03:31 PM, Dharmesh Kamdar wrote:
> So, my question is : even if we mention 
>                              features "2 pg_init_retries 50" 
> 
> why are we seeing " features='3 queue_if_no_path pg_init_retries 50' 
> hwhandler='1 rdac' wp=rw" in the multipath -ll output ?
> 
> 1) Where is this "3" coming from  ? and what is it's significance ?? 

It's the count if items to parse on the rest of the features line.

> 2) Is this "3" next to the features in "multipath -ll" output as expected (even 
> though we mention "2 pg_init_retries 50" ) in our multipath.conf ??

The format of the features field is:

FeatureCount# Feature/param0 Feature/param1 ... Feature/paramN

The 3 indicates three features/parameters. The first is "queue_if_no_path"
(which is implied by the "no_path_retry 30" in your device block - no_path_retry
requires the queue_if_no_path feature be enabled at the device-mapper level).
The 2nd and 3rd are the pg_init_retries feature and its parameter.

Regards,
Bryn.