Hey, thanks!

I tried the multipathing part you had down there and I couldn't get it to 
work... I did find that this worked though

#I pick a victim device
multipath -ll
...
mpathax (35000cca2680a8194) dm-49 HGST    ,HUH721010AL5200
size=9.1T features='0' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=1 status=enabled
  |- 1:0:10:0   sdj     8:144   active ready running
  `- 11:0:9:0   sddy    128:0   active ready running
#then I remove the device
multipath -f mpathax
#and verify that it is gone
multipath -ll | grep mpathax
#then I run the following, which seems to rescan for devices.
multipath -v2
Apr 26 10:49:06 | sdj: No SAS end device for 'end_device-1:1'
Apr 26 10:49:06 | sddy: No SAS end device for 'end_device-11:1'
create: mpathax (35000cca2680a8194) undef HGST    ,HUH721010AL5200
size=9.1T features='0' hwhandler='0' wp=undef
`-+- policy='service-time 0' prio=1 status=undef
  |- 1:0:10:0   sdj     8:144   undef ready running
  `- 11:0:9:0   sddy    128:0   undef ready running
#then its back
multipath -ll mpathax
mpathax (35000cca2680a8194) dm-49 HGST    ,HUH721010AL5200
size=9.1T features='0' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=1 status=enabled
  |- 1:0:10:0   sdj     8:144   active ready running
  `- 11:0:9:0   sddy    128:0   active ready running

I still need to test it fully once I get the whole stack up and running, but 
this seems to be a step in the right direction.


w/r,
Kurt

________________________________
From: Jongwoo Han <[email protected]>
Sent: Friday, April 26, 2019 6:28 AM
To: Kurt Strosahl
Cc: [email protected]
Subject: Re: [lustre-discuss] ZFS and multipathing for OSTs

Disk replacement with multipathd + zfs is somewhat not convenient.

step1: mark offline the disk you should replace with zpool command
step2: remove disk from multipathd table with multipath -f <mpath id>
step3: replace disk
step4: add disk to multipath table with multipath -ll <mpath id>
step5:  replace disk in zpool with zpool replace

try this in your test environment and tell us if you have found anything 
interesting in the syslog.
In my case replacing single disk in multipathd+zfs pool triggerd massive udevd 
partition scan.

Thanks
Jongwoo Han

2019년 4월 26일 (금) 오전 3:44, Kurt Strosahl 
<[email protected]<mailto:[email protected]>>님이 작성:

Good Afternoon,


    As part of a new lustre deployment I've now got two disk shelves connected 
redundantly to two servers.  Since each disk has two paths to the server I'd 
like to use multipathing for both redundancy and improved performance.  I 
haven't found examples or discussion about such a setup, and was wondering if 
there are any resources out there that I could consult.


Of particular interest would be examples of the /etc/zfs/vdev_id.conf and any 
tuning that was done.  I'm also wondering about extra steps that may have to be 
taken when doing a disk replacement to account for the multipathing.  I've got 
plenty of time to experiment with this process, but I'd rather not reinvent the 
wheel if I don't have to.


w/r,

Kurt J. Strosahl
System Administrator: Lustre, HPC
Scientific Computing Group, Thomas Jefferson National Accelerator Facility

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--
Jongwoo Han
+82-505-227-6108
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