Christophe Varoqui wrote:
On Thu, May 04, 2006 at 05:08:41PM +0300, Erez Zilber wrote:
Hi,
I'm new to device mapper and trying to set a multipath target:
I'm connected to the same LUN over iSCSI in 2 paths:
Here's the output of sg_map:
sg_map -i -x
/dev/sg0 3 0 0 0 0 /dev/sda DotHill SANnet II FC 411I
/dev/sg1 4 0 0 0 0 /dev/sdb DotHill SANnet II FC 411I
I ran the following command:
multipath 2 round-robin 1 0 /dev/sda round-robin 1 0 /dev/sdb
Just start multipathd
or run multipath without params
If I understand correctly, the 1st priority group contains /dev/sda. The
2nd priority group contains /dev/sdb. If /dev/sda fails, traffic should
automatically move to /dev/sdb. Is that right?
Here's the out put of multipath -l:
3600c0ff00000000007c1d121c397f503
[size=10 GB][features=0][hwhandler=0]
\_ round-robin 0 [prio=0][active]
\_ 3:0:0:0 sda 8:0 [active][undef]
\_ round-robin 0 [prio=0][enabled]
\_ 4:0:0:0 sdb 8:16 [active][undef]
What does 8:0 & 8:16 mean? What is 3600c0ff00000000007c1d121c397f503?
8:0 & 8:16 are paths major:minor numbers
3600c0ff00000000007c1d121c397f503 is the multipath name.
consider activating the fancy naming option in the config file.
Now, assuming that what I did so far is ok, how do I use the multipath
device? Do I use /dev/sda (or /dev/sdb)?
You should use /dev/mapper/3600c0ff00000000007c1d121c397f503
Regards,
cvaroqui
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Thanks. It seems to work now. Anyway, I have some more questions:
1. Was it wrong to run 'multipath 2 round-robin 1 0 /dev/sda
round-robin 1 0 /dev/sdb'?
2. If I don't supply any parameters, how does the dm know which
devices are the same physical device (that /dev/sda & /dev/sdb are
the same physical device)?
3. How are the priority groups defined if no parameters are supplied?
4. What is the timeout for a device that has failed? When does the dm
move to the next priority group?
Thanks
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____________________________________________________________
Erez Zilber | 972-9-971-7689
Software Engineer, Storage Team
Voltaire – _The Grid Backbone_
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www.voltaire.com <http://www.voltaire.com/>
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