[dm-devel] About using multipath in SLES 10

[Erez Zilber]

> > I understand that sdc & sdd are mapped to dm-1. However, I don't
> > understand how to use dm-1. For example, I can't run INQUIRY on it:
> >
> > seed1:~ # sg_inq /dev/dm-1
> > Both SCSI INQUIRY and fetching ATA information failed on /dev/dm-1
> 
> All things that work on /dev/sdc may not work on /dev/dm-1. You should
> use /dev/sdc instead of /dev/dm-1 for those cases. You should be able to
> use /dev/dm-1 for normal I/O (like dd, mounting etc.)

I understand. I've tried disktest, and it work ok. I have another question - I'm running a single iSCSI initiator against 2 iSCSI target. I started disktest on /dev/dm-1 and after a few seconds, I disconnected the primary target. It took ~2 minutes until it failed over to the secondary device. During these ~2 minutes, it seemed that disktest is still reading data from the target, just slower. That's very strange. After failover was completed, I was able to use the secondary device.
 
I have 2 questions:

1.	
	Which parameter in  multipath.conf do I need to change in order to failover in a few seconds? Is it polling_interval? I saw that the default value is 5 seconds, which should be ok.
2.	
	Before multipath decided that it needs to failover, why did I see that traffic is still running? It had no device to work with at that time.

Thanks,

Erez

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