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Old 07-11-2011, 03:34 PM
Mikhail Shevyakov
 
Default Wrong behaviour of multipathing on Active/Passive storage array

Hello!

I try to configure multipathing for Active/Passive storage and I have a problem with this:

when paths are switched (Active->Passive, Passive->Active) all read/write operations

are suspended. When paths switches back read/write resumes.

Following is the configuration:



# less /etc/multipath.conf

defaults {
user_friendly_names yes
prio alua
path_checker tur
no_path_retry 10
fast_io_fail_tmo 5
polling_interval 10
selector "round-robin 0"
path_grouping_policy multibus
rr_min_io 100
failback immediate
}




# multipath -ll
mpathb (0AvroRAIDDVAS 000000000000000097f62ae1) dm-0 AvroRAID,DVAS
size=683G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=5 status=active
|- 7:0:0:0 sdc 8:32 active ghost running
* `- 9:0:0:0 sdd 8:48 active ready* running

This is output of st_turs:

# sg_turs -v /dev/sdd
test unit ready cdb: 00 00 00 00 00 00
# sg_turs -v /dev/sdc
test unit ready cdb: 00 00 00 00 00 00
test unit ready: Fixed format, current; Sense key: Not Ready
Additional sense: Logical unit not accessible, target port in standby state
Info fld=0x0 [0]
device not ready

And REPORT TARGET PORT GROUPS output:

#sg_rtpg /dev/sdd
Report target port groups:
target port group id : 0x1 , Pref=1
target port group asymmetric access state : 0x00
T_SUP : 0, O_SUP : 0, U_SUP : 1, S_SUP : 1, AN_SUP : 0, AO_SUP : 1
status code : 0x02
vendor unique status : 0x00
target port count : 02
Relative target port ids:
0x01
0x02
#sg_rtpg /dev/sdc
Report target port groups:
target port group id : 0x2 , Pref=0
target port group asymmetric access state : 0x02
T_SUP : 0, O_SUP : 0, U_SUP : 1, S_SUP : 1, AN_SUP : 0, AO_SUP : 1
status code : 0x02
vendor unique status : 0x00
target port count : 04
Relative target port ids:
0x01
0x02
0x03
0x04

I used dd to write on the dm device:

#dd if=/dev/zero of=/dev/dm-0 oflag=direct bs=1M

Everything works fine untill paths are switched. dd stops, turs output:

# sg_turs -v /dev/sdd
test unit ready cdb: 00 00 00 00 00 00
# sg_turs -v /dev/sdc
test unit ready cdb: 00 00 00 00 00 00
test unit ready: Fixed format, current; Sense key: Not Ready
Additional sense: Logical unit not accessible, target port in standby state
Info fld=0x0 [0]
device not ready

REPORT TARGET PORT GROUPS output:

# sg_rtpg /dev/sdd
Report target port groups:
target port group id : 0x1 , Pref=0
target port group asymmetric access state : 0x02
T_SUP : 0, O_SUP : 0, U_SUP : 1, S_SUP : 1, AN_SUP : 0, AO_SUP : 1
status code : 0x02
vendor unique status : 0x00
target port count : 02
Relative target port ids:
0x01
0x02
# sg_rtpg /dev/sdc
Report target port groups:
target port group id : 0x2 , Pref=1
target port group asymmetric access state : 0x00
T_SUP : 0, O_SUP : 0, U_SUP : 1, S_SUP : 1, AN_SUP : 0, AO_SUP : 1
status code : 0x02
vendor unique status : 0x00
target port count : 04
Relative target port ids:
0x01
0x02
0x03
0x04

As you can see paths' states are switched.Output of multipath:

# multipath -ll
mpathb (0AvroRAIDDVAS 000000000000000097f62ae1) dm-0 AvroRAID,DVAS
size=683G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=5 status=enabled
|- 7:0:0:0 sdc 8:32 failed ready running
* `- 9:0:0:0 sdd 8:48 failed ghost* running


So states of the paths are changed but multipath for some reason fails both paths.
Is something wrong with my config or is it a bug in multipath?
Could you help me with this problem?

Regards
Mikhail Shevyakov




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Old 07-11-2011, 06:41 PM
Christophe Varoqui
 
Default Wrong behaviour of multipathing on Active/Passive storage array

On lun., 2011-07-11 at 19:34 +0400, Mikhail Shevyakov wrote:
> Hello!
> I try to configure multipathing for Active/Passive storage and I have
> a problem with this:
> when paths are switched (Active->Passive, Passive->Active) all
> read/write operations
> are suspended. When paths switches back read/write resumes.
> Following is the configuration:
>
Active/passive arrays should not use a 'multibus' grouping policy. You
should have 2 paths groups. And a hardware handler to signal the array
controllers about path group switching.

Your array seems to support alua, so you should seed your config with a
'device' config block from another alua-supported array.

Bye.

> # less /etc/multipath.conf
> defaults {
> user_friendly_names yes
> prio alua
> path_checker tur
> no_path_retry 10
> fast_io_fail_tmo 5
> polling_interval 10
> selector "round-robin 0"
> path_grouping_policy multibus
> rr_min_io 100
> failback immediate
> }
>
> # multipath -ll
> mpathb (0AvroRAIDDVAS 000000000000000097f62ae1) dm-0 AvroRAID,DVAS
> size=683G features='1 queue_if_no_path' hwhandler='0' wp=rw
> `-+- policy='round-robin 0' prio=5 status=active
> |- 7:0:0:0 sdc 8:32 active ghost running
> `- 9:0:0:0 sdd 8:48 active ready running
>
> This is output of st_turs:
>
> # sg_turs -v /dev/sdd
> test unit ready cdb: 00 00 00 00 00 00
> # sg_turs -v /dev/sdc
> test unit ready cdb: 00 00 00 00 00 00
> test unit ready: Fixed format, current; Sense key: Not Ready
> Additional sense: Logical unit not accessible, target port in standby state
> Info fld=0x0 [0]
> device not ready
>
> And REPORT TARGET PORT GROUPS output:
>
> #sg_rtpg /dev/sdd
> Report target port groups:
> target port group id : 0x1 , Pref=1
> target port group asymmetric access state : 0x00
> T_SUP : 0, O_SUP : 0, U_SUP : 1, S_SUP : 1, AN_SUP : 0, AO_SUP : 1
> status code : 0x02
> vendor unique status : 0x00
> target port count : 02
> Relative target port ids:
> 0x01
> 0x02
> #sg_rtpg /dev/sdc
> Report target port groups:
> target port group id : 0x2 , Pref=0
> target port group asymmetric access state : 0x02
> T_SUP : 0, O_SUP : 0, U_SUP : 1, S_SUP : 1, AN_SUP : 0, AO_SUP : 1
> status code : 0x02
> vendor unique status : 0x00
> target port count : 04
> Relative target port ids:
> 0x01
> 0x02
> 0x03
> 0x04
>
> I used dd to write on the dm device:
>
> #dd if=/dev/zero of=/dev/dm-0 oflag=direct bs=1M
>
> Everything works fine untill paths are switched. dd stops, turs output:
>
> # sg_turs -v /dev/sdd
> test unit ready cdb: 00 00 00 00 00 00
> # sg_turs -v /dev/sdc
> test unit ready cdb: 00 00 00 00 00 00
> test unit ready: Fixed format, current; Sense key: Not Ready
> Additional sense: Logical unit not accessible, target port in standby state
> Info fld=0x0 [0]
> device not ready
>
> REPORT TARGET PORT GROUPS output:
>
> # sg_rtpg /dev/sdd
> Report target port groups:
> target port group id : 0x1 , Pref=0
> target port group asymmetric access state : 0x02
> T_SUP : 0, O_SUP : 0, U_SUP : 1, S_SUP : 1, AN_SUP : 0, AO_SUP : 1
> status code : 0x02
> vendor unique status : 0x00
> target port count : 02
> Relative target port ids:
> 0x01
> 0x02
> # sg_rtpg /dev/sdc
> Report target port groups:
> target port group id : 0x2 , Pref=1
> target port group asymmetric access state : 0x00
> T_SUP : 0, O_SUP : 0, U_SUP : 1, S_SUP : 1, AN_SUP : 0, AO_SUP : 1
> status code : 0x02
> vendor unique status : 0x00
> target port count : 04
> Relative target port ids:
> 0x01
> 0x02
> 0x03
> 0x04
>
> As you can see paths' states are switched.Output of multipath:
>
> # multipath -ll
> mpathb (0AvroRAIDDVAS 000000000000000097f62ae1) dm-0 AvroRAID,DVAS
> size=683G features='1 queue_if_no_path' hwhandler='0' wp=rw
> `-+- policy='round-robin 0' prio=5 status=enabled
> |- 7:0:0:0 sdc 8:32 failed ready running
> `- 9:0:0:0 sdd 8:48 failed ghost running
>
>
> So states of the paths are changed but multipath for some reason fails both paths.
> Is something wrong with my config or is it a bug in multipath?
> Could you help me with this problem?
>
> Regards
> Mikhail Shevyakov
>


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dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel
 

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