Memory Optimized Mode or advanced ecc mode on hosts ?

Windows 2008 R2 (to be upgraded to Windows 2012 very soon) Hyper-V cluster (8 hosts all Poweredge R710)

We're about to add 6x 16GB  PC3-10600 DDR3-1333MHz ECC Registered certified DIMMs on each server.  

Is it better to enable (install the dimms in order to)  Memory Optimized Mode or advanced ecc mode?  The performance is not a real issue.  Besides, I don't think the performance gap is that important.  Reliability is important.  

I think SDDC is available in optimized mode when 4x memory DIMM are used, is that right?

I would like to hear your advices and thoughts on...

Thanks
quadrumaneAsked:
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PowerEdgeTechIT ConsultantCommented:
If reliability is your primary concern, then turn on Advanced ECC, which implements Intel's chipkill technology.  Optimizer Mode is for performance.
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quadrumaneAuthor Commented:
Can Advanced ECC can be turned on if the memory DIMMS are used on all channels (6 channels , one DIMM installed on a socket of each channel)  ?  This is the part I'm not sure about.  In one of the to many documents I've been reading it says Optimized configuration can be used as Advanced ECC.  

Thanks
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footechCommented:
With Advanced ECC mode the channel farthest from each processor cannot be used.  This equates to A1,4,7 and B1,4,7.  If you have DIMMS in every channel, it will automatically change to Memory Optimized mode.

You are correct about SDDC w/ Optimizer.

The best documents IMO are the R710 Owner's Manual and the R710 Tech Guidebook.  They both spell out the guidelines for DIMM population.

I go with the Advanced ECC mode whenever possible.  But sometimes the modules on hand or the capacity needed dictate a change to Optimizer mode.
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quadrumaneAuthor Commented:
I understand.  But you said I'm correct about SDDC w/ Optimizer.  But as far as I understand the concept to switch to SDDC the channel farthest from each processor cannot be used. But I need all channels to enable Optimizer mode, including the farthest..  

How come?

Thanks again
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footechCommented:
Optimizer supports SDDC for x4 modules.  Advanced ECC supports SDDC for x4 and x8 modules.  Not all channels have to be populated with Optimizer.  Take a look at the Owner's Manual (can be found with a quick search) and it will show you sample configurations that confirm this.
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quadrumaneAuthor Commented:
I'm reading the manual.  All configuration are listed but SDDC w/ Optimizer.  

I have x4 modules.  The 16GB DIMMS have been inserted in A1, A2, A3, B1, B2, B3  

The BIOS is automatically detecting Optimizer mode.   In the BIOS only the compatible configurations are listed in the memory section.   I switched to Advanced ECC.  But I've got  warnings.  As a result only 64GB is usable of 96GB.  

Thanks again.
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quadrumaneAuthor Commented:
I called Dell.

SDDC w/Optimizer is possible.  But not all the memory will be available.  I will switch to Advanced ECC without Optimizer.  

Thanks a lot
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footechCommented:
SDDC isn't a mode, it's a feature of a mode.  So when you've selected Optimizer, you now have the x4 SDDC.

With A1 and B1 populated, you won't be able to use Advanced ECC mode (or if you select it, those slots won't be used), that's why it's detecting Optimizer mode.

When you said you were adding 6 x 16GB modules, is that all that's going to be in your server or are you adding those 6 to however many modules are already in there?  If only the 6 will be there, you will populate A2, A3, A5 and B2, B3, B5 for Advanced ECC mode.
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quadrumaneAuthor Commented:
Well that's really enlightening.  

I'm having 6 x 16GB  I removed 18x 4GB from the servers.  So I will be using 6 x 16GB.  More memory will be added if it's required in the future.  

SDDC feature enabled with Optimizer mode vs Advanced ECC mode.  What is the difference?  

SDDC w/ Optimizer looks like an Advanced ECC mode with better performance for x4 modules.  On another hand, DIMMs based on x8 modules will be used to achieve only Single Device Data Correction.  

Thanks a lot !
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