Two Linux nodes are presented the same storage; but the LUNs are discovered/named differently.

[Sanjay Chakraborty]

Yes you need to setup multipth and give user friendly name. The doc
you can find in redhat documentation.

On Mon, Sep 19, 2011 at 5:11 PM, Geofrey Rainey
<Geofrey.Rainey at tvnz.co.nz> wrote:
> 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 at redhat.com [mailto:redhat-list-bounces at 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 at 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 at 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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-- 
Regards.
Sanjay Chakraborty