[dm-devel] RE: Temporarily squelching multipathd errors

[Daniel Keisling]

> -----Original Message-----
> From: Konrad Rzeszutek [mailto:konrad at virtualiron.com] 
> Sent: Friday, January 16, 2009 3:29 PM
> To: Daniel Keisling
> Cc: device-mapper development
> Subject: Re: [dm-devel] RE: Temporarily squelching multipathd errors
> 
> On Fri, Jan 16, 2009 at 02:29:40PM -0600, Daniel Keisling wrote:
> > Right now I'm deleting the LUN, immediately creating a new LUN, and
> 
> > presenting it back to the system with the same SCSI ID.  
> Since it's a
> 
> > snapshot, the LUN geometry is always the same.  I've tried 
> unpresenting
> 
> > the LUN, deleting the SCSI devices, recreating/presenting 
> the LUN, and
> 
> > then doing a SCSI rescan, but the multipath errors are 
> always there.  
> 
> > 
> 
> > Here's the multipath listings.  I am only deleting/presenting the
> 
> > "mpath33" map, but you can see the multipath errors and the 
> other paths
> 
> 
> How are you 'deleting' the mpath33 map? Are you using 
> 'dmsetup remove mpath33'
> ?


No, I am telling the storage unit to delete the LUN.  In this test, I:

A) Unmount the filesystem
B) Tell the storage system to delete the LUN (which unpresents it,
obviously)
C) Tell the storage system to make a new LUN using the same WWID and
SCSI ID as before
D) Present the LUN

Since all this takes around 20 seconds, I can immediately mount the LUN
again on the server.

> 
> > having a fault:
> 
> > 
> 
> > Unmounting /dev/mapper/mpath33p1...
> 
> > Multipath listing before LUN is deleted...
> 
> > cred_arch (3600508b400106fcd0000700011f30000) dm-52 HP,HSV210
> 
> > [size=5.0G][features=1 queue_if_no_path][hwhandler=0]
> 
> 
> ..snip ..
> > 
> 
> > 
> 
> > Multipath listing after LUN is deleted and before LUN is added...
> 
> 
> I am not seeing how you are deleting the SCSI device of the node.
> Are you doing 'echo 1 > /sys/block/sdab/device/delete' for all
> of those block-devices that match the 'deleted LUN'?
> 


No, I am not.  I have before, but it didn't seem to help.



> 
> .. snip ..
> > 
> 
> > 
> 
> > Multipath output after LUN is added...
> 
> 
> How are you doing a SCSI rescan?
> 
> 

I'm not in this test.  Since all this takes around 20 seconds, I can
immediately mount the LUN again on the server with any SCSI devices
permanently disappearing.

Would you like me to:

A) Umount the filesystem
B) Perform a 'dmsetup remove mpath33'
C) Delete all SCSI devices via /sys/block/$device/delete
D) Tell the storage unit to unpresent and delete the LUN
E) Optionally do a SCSI rescan to clear everything out
F) Tell the storage unit to create the LUN with the same WWID and SCSI
ID
G) Perform a SCSI rescan
H) Do a multipath -v3 to get the maps back (?)
I) Fsck and mount the filesystem?

I believe I get the same results as what I pasted, but will prove it if
need be.

BTW, I do a SCSI rescan with the HP Fibreutils package (hp_rescan -a),
which basically does a "echo "- - -" >
/sys/class/scsi_host/${INST}/scan" and removes devices with "echo "scsi
remove-single-device $INST 0 $j $k" > /proc/scsi/scsi"

Thanks,

Daniel

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