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-   -   Two Linux nodes are presented the same storage; but the LUNs are discovered/named differently. (http://www.linux-archive.org/red-hat-linux/577708-two-linux-nodes-presented-same-storage-but-luns-discovered-named-differently.html)

Geofrey Rainey 09-19-2011 09:11 PM

Two Linux nodes are presented the same storage; but the LUNs are discovered/named differently.
 
You need to set up multipathing. Oracle Metalink has good documentation on this, check out note id# 564580.1

It has sections such as "A Bit About Udev and Device Name Persistency".

Regards,
Geofrey Rainey.


-----Original Message-----
From: redhat-list-bounces@redhat.com [mailto:redhat-list-bounces@redhat.com] On Behalf Of unix syzadmin
Sent: Tuesday, 20 September 2011 2:48 a.m.
To: General Red Hat Linux discussion list
Subject: Re: Two Linux nodes are presented the same storage; but the LUNs are discovered/named differently.

Hi Matt,

Thanks.
I am an UNIX admin; not a DBA.
>From what I know; DBA plan to use ASM to manage the storage.

However; my question is still valid.
If two nodes are presented the same storage; why would a EMC LUN on node1 be discovered and named differently on node2?

node1:

emcpowera --> lun# 1346

# ls -ld /dev/emcpowera
brw-r----- 1 root disk 120, 0 Sep 16 16:17 /dev/emcpowera


node2:
emcpowerg --> lun#1346

# ls -ld /dev/emcpowerg
brw-r----- 1 root disk 120, 96 Sep 16 16:23 /dev/emcpowerg


>From the above "emcpowera" on node1 is called "emcpowerg" on node2.
The LUN number shown in powerpath is same for both of them.
Also the minor and major device numbers for the LUNs are different on both the nodes.

It would be better if LUN# 1346 would be discovered as" ecmpowera" on both the nodes with the same minor/major numbers.
I know that most of these are going to be used by ASM and I don't have to worry.

But if there was a problem with LUN#1346; i would have to deal with the two different device names in both the nodes.
This is going to be in production soon and down the line there might be more storage that might get added. So for troubleshooting and maintenance I think it would help if these LUNs were named/discovered similarly on both the nodes.

Thanks,



On Mon, Sep 19, 2011 at 9:54 AM, Matty Sarro <msarro@gmail.com> wrote:

> You can configure the names used if you want, but you may want to
> consider using oracle ASM - then it won't matter what the disks are
> named, only what the ASM volume is called. This would only be done on
> the first server, and the ASM data should be read by the second server
> automatically.
> -Matt
>
> On Mon, Sep 19, 2011 at 9:48 AM, unix syzadmin
> <unixsyzadmin@gmail.com>
> wrote:
> > Hi,
> >
> > We are setting up 2 RHEL 5.6 server to be used in the oracle RAC
> > cluster environment.
> >
> > We have about 25 X 200G EMC LUNs presented to the servers.
> > Since it is the RAC cluster; same LUNs are presented to both the nodes.
> >
> > However I see that the names for the LUNs are different on both the
> servers.
> > for example: "emcpowera" on node1 is discovered as" emcpowerg" in node2.
> >
> >
> > Any suggestions/ideas?
> > Thanks,
> > --
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