RE: [Linux-cluster] General FC Question

[Kovacs, Corey J.]

One more thing, when using more than one path (basically anyu san setup) the
device
mappings will wrap around for every path, so for two paths... single hba,
dual controller..


three disks will look like this...

disk1=/dev/sda
disk2=/dev/sdb
disk3=/dev/sdc
disk1=/dev/sdd
disk2=/dev/sde
disk3=/dev/sde 

and four like this..

disk1=/dev/sda
disk2=/dev/sdb
disk3=/dev/sdc
disk4=/dev/sdd
disk1=/dev/sde
disk2=/dev/sde 
disk3=/dev/sdf
disk4=/dev/sdg


Or for dual hba, dual controller (4 paths)


disk1=/dev/sda
disk2=/dev/sdb
disk3=/dev/sdc
disk4=/dev/sdd
disk1=/dev/sde
disk2=/dev/sde 
disk3=/dev/sdf
disk4=/dev/sdg
disk1=/dev/sdh
disk2=/dev/sdi
disk3=/dev/sdj
disk4=/dev/sdk
disk1=/dev/sdl
disk2=/dev/sdm 
disk3=/dev/sdn
disk4=/dev/sdo

etc...

Cheers

With the Qlogic drivers in failover mode, you'll get this..

disk1=/dev/sda
disk2=/dev/sdb
disk3=/dev/sdc
disk4=/dev/sdd

even though there are multiple paths



Corey

-----Original Message-----
From: linux-cluster-bounces at redhat.com
[mailto:linux-cluster-bounces at redhat.com] On Behalf Of Kovacs, Corey J.
Sent: Tuesday, September 26, 2006 7:38 AM
To: isplist at logicore.net; linux clustering
Subject: RE: [Linux-cluster] General FC Question

You don't say which FC cards you are using but if it's qlogic, then the
driver can be set to combine the devices. Basically whats happened is that
your machine is picking up the alternate path to the device, which is a
perfectly valid thing to do, it's just not what you need at this point. It
may be as simple as your

secondary controller actually has the lun you are trying to access. To work
around yo might just be able to reset the seconday controller and force the
primary to take over the LUN. This happens quite a bit depending on your
setup. The Qlogic drivers, when setup for failover, will coelesce the devices
into a single device by the WWID of the LUN. If that's not an option, then
try the multipath tools support in
RHEL4.2
or above. You won't be using the /dev/sd{a,b,c,...} devices, rather it'll be
/dev/mpath/mpath0 etc, or whatever you set them to instead.

Even without failover, the latest Qlogic drivers will make both paths active
so that you never end up with a dead path upon boot up.


Hope this helps.


Corey

-----Original Message-----
From: linux-cluster-bounces at redhat.com
[mailto:linux-cluster-bounces at redhat.com] On Behalf Of isplist at logicore.net
Sent: Monday, September 25, 2006 11:18 AM
To: linux-cluster
Subject: [Linux-cluster] General FC Question

After adding storage, my cluster comes up with different /dev/sda, /dev/sdb,
etc settings. My initial device now comes up as sdc when it used to be sda. 

Is there some way of allowing GFS to see the storage in some way that it can
know which device is which when I add a new one or remove one, etc?

Hard loop ID's on the FC side I think but is there anything on the GFS side?

Mike



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