DELL MD3220 사용자 설명서

Configuration: Device Mapper Multipath for Linux

How can I check if multipathd 

is running?

Run the following command
/etc/init.d/multipathd status

Why does the multipath 
–ll

 

command output not 

show any devices?

First verify if the devices are discovered or not. The 

command #cat /proc/scsi/scsi displays all 

the devices that are already discovered. 
Then verify the multipath.conf to ensure that it is 

been updated with proper settings. 
After this, run multipath. Then run multipath 
–ll, the new devices should be displayed.

Why is a newly-mapped LUN 

not assigned a multipathing 

device node?

Run “rescan_dm_devs” in any directory. This should 

bring up the devices.

I have no LUNs mapped before. 

Then I map a few LUNs. After 

running rescan-scsi-
bus.sh, LUN 0 does not show 

up. 

Run rescan_dm_devs instead of rescan-
scsi-bus for LUN 0 reconfiguration.

I removed a LUN, but the 

multipathing mapping is still 

present.

The multipathing device is still there after you 

remove the LUNs. Run multipath –f <device 

node for the deleted LUN> to remove the 

multipathing mapping. For example, if device 

devices related with /dev/dm-1 is deleted, you must 

run multipath –f /dev/dm-1 to remove 

/dev/dm-1 from DM mapping table. If multipathing 

daemon is stopped/restarted, run multipath –F 

to flush out all stale mappings.

Failback does not happen as 

expected with the array.

Sometimes the low level driver cannot auto-detect 

devices coming back with the array. Run 
rescan_dm_devs to do a rescan of the host server 

SCSI bus and re-aggregate devices at multipathing 

layer.

book.book  Page 175  Monday, June 21, 2010  11:00 AM