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Why 8 ATTO bridges? Fabric Metrocluster with SAS stacks

Looking and reading at documentation regarding usage of ATTO SAS-FC bridge on Metrocluster I've always read about the need to have 4 bridges (as in the pic here) to connect and double the path to the stack SAS up to completation of one of this stack (seven DS4243 shelves).

I should setup a fabric MC where I will use both SAS and SATA disks in my DS4243 shelves: exactly as in the pic with one site with both 1xSAS+1xSATA shelves and the second site only with 1xSAS.

It now happens that configuring in PE/CE the needed hardware it give me EIGHT bridges for somewhere somebody says that this is best practice to have separate stack for SAS and SATA...what?!? This violates the principle that the SAS backend can do: a multiplexed one of four 3 Gbps links each

As far I know a stack SAS can be formed by both SAS and SATA disks mixing the DS4243 (up to ten shelves) and the ATTO manual too repeat this. No issue at all.

Why should my customer but other 4 ATTO bridges (9000 € each price list!)?

Regards

Re: Why 8 ATTO bridges? Fabric Metrocluster with SAS stacks

Hi,

I think technically speaking you are correct.

PartnerEdge always used to have its own ways of 'best practices' around different things, like throwing in extra SAS HBAs on 3200 platforms.

I believe you can always build MetroCluster setup manually (i.e. as a non-MC configuration) & add additional components via "Add parts" - just run the outcome through your NetApp resource to make sure they are happy with that as well!

Regards,

Radek

Re: Why 8 ATTO bridges? Fabric Metrocluster with SAS stacks

Hi,

thanks for prompt answer. I agree with you but I would prefer that this kind of answer come from some NetApp representative.

Re: Why 8 ATTO bridges? Fabric Metrocluster with SAS stacks

We recently raised exactly the same query with the NetApp Partner Helpdesk this week and received the reply below.

As an observation, if there is any single person within the channel whose advice I would trust,  it is Radek.

Hope this helps,

Pete Springfield

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Question -

.... The challenge is that the specification it spits out includes 8 of the new SAS Bridges, my assumption is that you can mix both SAS and SATA disk within a stack (pg 19 of the attached PDF) and would only require 4 of the SAS bridges in total.

Answer -

yes, that's correct. SAS and SATA shelves can be mixed in the same stack, which would require only four SAS Bridges in total.

According to the MetroCluster Product Frequently Asked Questions,
MC (DOT 8.1.0 release) do support SAS and SATA drives in separate DS4243 shelves (but in the same stack). However, this is not supported as a configured system at POS. If someone wants a combination of SAS and SATA drives with DS4243 the same stack, they will have to order an MC configuration with SAS drives  and then order DS4243 with SATA drives as add-on or vice-versa.


I hope this answers your question.

Kind regards

NetApp SE Helpdesk
Phone:    +44 207 280 3754
partner-helpdesk-uk@netapp.com
www.netapp.com

Re: Why 8 ATTO bridges? Fabric Metrocluster with SAS stacks

No doubts on Radek answer but the "official" channel is what I need to convince account that plays with configurator that I don't need all that stuff!

Many thanks

Re: Why 8 ATTO bridges? Fabric Metrocluster with SAS stacks

I'm with you there.

All the best, Pete

Re: Why 8 ATTO bridges? Fabric Metrocluster with SAS stacks

I'm in the process of buying a metro cluster solution. Today we've both SAS and SATA disks in the system. Our NetApp Partner advice us not to mix SAS and SATA in the same stack and came up with a solution including 8 ATTO 6500N bridges (exactly as the drawing in the gmilazzoitag posted earlier in the thread). But looking to the tech. spec the bridge has 2 SAS ports A & B. Can't I use both SAS ports in the bridge? port A for a stack of SAS disks and port B for a stack of SATA disks. Then it should be enough with 4 bridges. Or is that impossible?

Regards

Re: Why 8 ATTO bridges? Fabric Metrocluster with SAS stacks

No, you cannot use both SAS ports. You need 2 bridges per loop on each site.

Re: Why 8 ATTO bridges? Fabric Metrocluster with SAS stacks

OK, thanx for answer. Do you have any explenation why I can't use both ports? In what situation is it possible to use both ports then?

Re: Why 8 ATTO bridges? Fabric Metrocluster with SAS stacks

No, I do not have explanations. That’s what is supported by NetApp.