Re: multipath and san fabric

[James Smart <James.Smart@Emulex.Com>]

Yep - Ed caught my typo....  :)

-- james

Philip R. Auld wrote:
> Rumor has it that on Mon, Nov 13, 2006 at 02:39:08PM -0500 Edward Goggin said:
>> You may want to also cross connect across the 2 target
>> controllers (A,B) in case 2.  Doing so provides more
>> redundancy for asymmetric arrays and better resource
>> utilization in case of a failure of either an HBA or
>> target controller which would otherwise prevent
>> utilization of the other HBA or target controller
>> for that LU when load sharing I/O across multiple
>> paths.
>>
>> So the I_T nexus's for the 4 paths are:
>>
>> 	HBA1_TargetPort1
>> 	HBA1_TargetPort3
>> 	HBA2_TargetPort2
>> 	HBA2_TargetPort4
>>
> 
> That's exactly what James's example 2 describes. It's just 
> typo'd in the DM paths list. 
> 
> 
> 
>>> -----Original Message-----
>>> From: dm-devel-bounces@redhat.com 
>>> [mailto:dm-devel-bounces@redhat.com] On Behalf Of James Smart
>>> Sent: Monday, November 13, 2006 2:18 PM
>>> To: jslittl@hendricks.org; device-mapper development
>>> Subject: Re: [dm-devel] multipath and san fabric
>>>
>>> If the hba's are on different fabrics - why would you ever put an hba
>>> that is not in the fabric in a zone in that fabric ?  (e.g. 
>>> your second
>>> option makes no sense).
>>>
>>> If you are stating that the 2hba's are on different fabrics 
>>> (and in zones
>>> within those fabric) - but they are seeing the same Storage 
>>> device on both
>>> fabrics - then the dm config (note: I'm not talking about 
>>> zoning anymore)
>>> would have a path per I_T nexus. I state it this way to 
>>> account for dual-ported
>>> controllers, which may appear as separate targets, may exist 
>>> within the fabric.
>>>
>>> Example 1:
>>>    Fabric A contains HBA1 and TargetPort1. Typically a zone 
>>> would exist
>>>      within Fabric A that contains these 2 ports.
>>>    Fabric B contains HBA2 and TargetPort2. Typically a zone 
>>> would exist
>>>      within Fabric B that contains these 2 ports.
>>>    The storage array contains 2 controllers with 1 port per 
>>> controller, or
>>>      is a single controller with 2 ports. Either way, the two 
>>> ports are
>>>      TargetPort1 and TargetPort2, are on the same array, and 
>>> all storage
>>>      can be seen from any port.
>>>    --
>>>    This would have 2 DM paths.
>>>    The I_T nexus's are:
>>>       HBA1_TargetPort1
>>>       HBA2_TargetPort2
>>>
>>> Example 2:
>>>    Fabric A contains HBA1, TargetPort1, and TargetPort3. 
>>> Typically a zone
>>>      would exist within Fabric A that contains these 3 ports.
>>>    Fabric B contains HBA2, TargetPort2, and TargetPort4. 
>>> Typically a zone
>>>      would exist within Fabric B that contains these 3 ports.
>>>    The storage array contains 2 controllers, with 2 ports per 
>>> controller.
>>>      Meaning TargetPort1 and TargetPort2 are on controller A, 
>>> and TargetPort3
>>>      and TargetPort4 are on controller B. The ports are cross 
>>> connected on
>>>      the fabrics for redundancy. All storage can be seen from 
>>> any port.
>>>    --
>>>    This would ahve 4 DM paths
>>>    The I_T nexus's are:
>>>       HBA1_TargetPort1
>>>       HBA1_TargetPort2
>>>       HBA2_TargetPort3
>>>       HBA2_TargetPort4
>>>
>>> -- james
>>>
>>> John Little wrote:
>>>> Hi all
>>>>
>>>> Admittedly this is not the correct forum for this question 
>>> but I have googled 
>>>> this and the only people I have to ask around here are 
>>> people who won't touch 
>>>> it because it is Linux.
>>>>
>>>> My question is this:  I'm using SLES10 with two emulex 
>>> hbas, one connected to 
>>>> fabric a and one to fabric b.  When zoning the switch for 
>>> the hbas do I put 
>>>> in only one path to the fabric per hba or do I put in two, 
>>> one to each of the 
>>>> separate fabrics?
>>>>
>>>> Again I realize this is not exactly the correct forum but 
>>> since I couldn't 
>>>> find an answer anywhere else I figured you guys would be the most 
>>>> knowledgeable.  If there are some docs somewhere that you 
>>> could point me to I 
>>>> would appreciate it.
>>>>
>>>> John
>>>>
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>>>>
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>>>
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