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markwragge

71 Posts

1763

May 30th, 2007 08:00

How much time should it take for a powepath path to come back online?

We have installed powerpath v4.5.1 on Linux Redhat 4.0 U5. When a fibre path is removed from the HBA powerpath reports the path as dead. When the fibre cable is re-inserted it takes powerpath about 5 minutes to list the path as alive using powermt command. Is this the usual time for a linux path to come online?
Is is possible to present a new lun to linux without having to unmount the other emc disks and stop the fibre card - as stated in the powerpath documentation? Cna linux not rescan to find new luns like other OSs can?

dynamox

9 Legend

 • 

20.4K Posts

May 30th, 2007 19:00

i have been fairly successful rescanning for new luns on linux (2.6 kernel) by issuing:

echo ¿- - -¿ > /sys/class/scsi_host/hostx/scan

where hostx is going to be the name of the adapter on your system, you can get it by looking in /proc/scsi/qlaxxx. You will need to run this command for each adapter on the system. Also don't forget to run powermt config, powermt save (if you run PowerPath of course) ..after devices have been discovered.

rr_phx

26 Posts

May 30th, 2007 10:00

To ensure the Path is not going to go down and up within a short periods, it's normal for PowerPath to take 3-5 minutes to recover the Path. Could try "powermt restore" to see if that will wake it up faster.

Getting Linux to rescan has been a challange for awhile. But if take a look at EMC primus case "emc94679" it makes reference to the Emulex and QLogic Linux Tools.

Emulex
The Emulex Lun Scan Script can be downloaded from the Tools for the Emulex Driver for Linux page

Qlogic
The Qlogic FC HBA LUN Scan Utility can be downloaded from the Linux Utilities section of the EMC Approved Software: Symmetrix, CLARiiON and Celerra section.

Navin-Swn_9

66 Posts

May 31st, 2007 02:00

I've came acrosss a situation where LUN SCAN command rebooted the server. Good thing was it was part of a cluster and hence no business impact.
I am always more comfortable asking a business approval for reboot of the server (LINUX) when assigning or deassigining storage.
But in 95% cases linux can rescan the devices online as mentioned my other gentlemen.

Conor

341 Posts

June 18th, 2007 07:00

5 minutes for an auto-restore of a dead path is normal. The auto restore is run at a low priority (I/Os being serviced are much higher) In a busy environments it may take several hours for a path to auto-restore due to the IOs being given the priority. Normally 5 mins is about right for a restore.

Conor

341 Posts

April 16th, 2009 07:00

Sorry - there is no parameter that will speed-up the auto-restore... as you said a powermt config could be scripted to run once the scsi devices re-appear to the host...

Conor

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