CX500 - Direct Attach Question

Question

Hi,

Newbie question. I've been reading CLARiiON documentation for 2 days, and frankly, my head is spinning.

My employer has given me a CX500 (DPE2 plus one DAE2-ATA) and three Dell PowerEdge 1850 Blades, each blade with one HBA.

What we want to do is this:

Use two of the Dell Blades to create a 2 node Oracle 10g RAC database, this will run our transactional database. We want to plug the first blade into SP-A (Port 0) of the CX500 and plug the second blade into SP-A (Port 1).

The third Dell blade will be plugged into SP-B (Port 0). This blade will host another Oracle instance especially for our data warehouse.

This is for a new development environment we're trying to get off the ground.

Is this configuration possible? I'm currently looking at page 6-8 in the Storage Systems Configuration Planning Guide and it says:

"The minimum hardware required for shared-or-clustered direct
storage is two servers, each with two host bus adapters, and one
storage system with two SPs."

This sounds like I can't build a RAC because my servers only have one HBA each.

Can anyone offer any insight?

Many thanks.

Allen Ward · Answer

I agree that you should be using switches in there, but if you don't you will absolutely need two HBAs to avoid failures.

kelleg · Answer

Two other documents that you may want to look at are:

"CLARiiON Open Systems Configuration Guide"
"EMC CLARiiON Best Practice for Fibre Channel Storage"

Both of these provides good information on general setup and use.

Also, there is a White Paper:

"CLARiiON Initial Configuration¿Best Practices Planning"

And, the Host Connectivity Guides for the different operating systems.

Generally, for failover protection you need two HBAs in the host and two switches. This allows you to connect each HBA to both SPA and SPB - then is one SP or switch or HBA fails you have an alternate path to the LUNs.

glen k

Kiran3 · Answer

both above suggestions are valid, dot on.

if you want to continue in the current situation, or you would not want to hold up setup till new hbas are brought in, you may

1. put both hbas in one node and configure it for full redundancy (one hba in spa and other in spb, with powerpath) and then configure other host when hbas arrive.

2. connect one hba to spa and other on spb ...but your nodes will failover in case path to one sp fails before adding other hba...

Kiran3 · Answer

Is it possible to directly attach 3 servers (each with only one HBA) to a CX500?

yes, in theory you can direct-attach as many hbas as many ports are there...so if you have one hbas in each system, you can connect 4 hosts i guess (2 ports per sp on cx500)

but make sure that if hbas are connected to spa, then luns are owned by spa only otherwise host will not see it.

SYDNEY2 · Answer

Hi, (I'm the author of the original question).

Thanks for your replies so far. I want to clarify/emphasize that this will be an in-house DEV system, not a production system and we're not interested in failover right now. If it is avoidable, management does not want to purchase a switch or any more HBA (for now).

I just need to know:

Is it possible to directly attach 3 servers (each with only one HBA) to a CX500?

Thanks.

SYDNEY2 · Answer

Thank you very much.

kelleg · Answer

Also, make sure that you set the failover mode to 0 (zero) - the default sometimes gets set to 1 (for PowerPath) and it allows an HBA on SPA to 'see' LUNs on SPB.glenk

Kiran3 · Answer

will setting autotrespass off also help in here? we do not want sp to trespass the lun here on its own since there is not going to be alternate path on peer sp

kelleg · Answer

autotrespass should be off by default when you create a new LUN, do not set it on.glenk

SYDNEY2 · Answer

Thanks everyone, for all your input. Much appreciated.

CLARiiON

CX500 - Direct Attach Question

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