Clear multipath metadata from old ZFS disk?

[mevans336]

I was gifted several 1TB disks from an old FreeNAS array we used at work. Each disk was in an MD1220 chassis and had a multipath connection to two controllers.

When I popped these disks into my FreeNAS 11.3-RC1 server (single controller, no multipath), they show up, but when I try to do anything with them (add them to an array, wipe them) FreeNAS tries to access them via their old multipath/disk# device. I've tried just about every variation of wiping them, dd to kill the first 512 bytes, dd to kill the last 1000 sectors, booting off gparted and deleting the GPT partition, etc. Nothing worked. Trying to interact with them in any manner caused FreeNAS to attempt to access them via their old multipath/disk# designations.

I stumbled across gmultipath and manually mapped the da# to what FreeNAS thought the multipath/disk# should be and voila, FreeNAS could communicate with them, albeit it complains the multipath is degraded (understandably). I thought perhaps after manually mapping them a 'gmultipath destroy' would clear the metadata, but the drives just revert to the previous behavior.

I'm not seeing any performance issues and other than the mild annoyance of the alerts in the GUI, things are fine, but does anyone know why I was unable to get these disks out of multipath mode, clear the metadata, or whatever might have been the root cause?

 

[Johnny Fartpants]

Code:

gmultipath destroy disk1

Where 'disk1' is the multipath name.

Code:

gmultipath list

will show you a list of your multipath devices including the name if you don't know it.

 

[mevans336]

Code:

gmultipath destroy disk1

Where 'disk1' is the multipath name.

Code:

gmultipath list

will show you a list of your multipath devices including the name if you don't know it.

I tried that, gmultipath list didn't show any multipath devices, even though the GUI was reporting them as multipath. Also, as I noted, after manually mapping them with gmultipath and confirming they were accessible and useable, gmultipath destroy just reverted them to the old behavior where the GUI thinks they are multipath devices, but there is no corresponding /dev/multipath/disk# device.

 

[Johnny Fartpants]

I'm guessing you've tried rebooting after the above?

 

[mevans336]

I'm guessing you've tried rebooting after the above?

Indeed. I even tried to mv the geom_multipath.ko module to prevent multipath from loading, but they were still detected as multipath devices. Maybe a bug in 11.3-RC1?

 

[Johnny Fartpants]

I would be tempted to boot of an installer and at that stage drop to the CLI and do a gmultipath list and if it shows a gmultipath destroy disk1 and then reboot into your system.

 

[Rabinovitch]

C

Code:

gmultipath destroy disk1

Where 'disk1' is the multipath name.

Code:

gmultipath list

will show you a list of your multipath devices including the name if you don't know it.

Can this damage GPT in any way?

 

[Johnny Fartpants]

Nope