Question about Memory Speed

[dashoe]

I'm upgrading the RAM on some Dell R710 servers. There are a number of possible configurations however the below excerpt from the user manual indicates that the ram will operate at specific speeds depending on how many modules (up to 3) are place in a channel. In the end I opted to use the larger modules with just one module per channel in order the achive the highest memory 1333 MHz rate. My question is how significant will the performance difference be? For example, if I add even more ram in the future, I'll have to drop to the 1067 MHz rate (would I be likely to notice it)? Note that these machines will be serving as hypervisiors not NAS units. I assume, from other post here, that for TrueNas maxing out the RAM will be beneficial even if it runs at a lower rate.

For single or dual-rank memory modules:
• One memory module per channel supports up to 1333 MHz.
• Two memory modules per channel supports up to 1067 MHz.
• Three memory modules per channel are limited to 800 MHz,
regardless of memory module speed.

 

[Davvo]

More RAM is better than faster RAM.

 

[MrGuvernment]

Unless you are running specific apps or services that require superfast memory speed, often to match a processor, you wont notice. For TrueNAS MOARRRRRRRRR is always better

 

[Ericloewe]

Note that these machines will be serving as hypervisiors

Dell R710 servers

Are you sure that's a good idea? They're a stone's throw away from being not viable with any modern hypervisor and they chew up a lot of power for a measly 12 cores.

 

[dashoe]

Are you sure that's a good idea? They're a stone's throw away from being not viable with any modern hypervisor and they chew up a lot of power for a measly 12 cores.

They do run around 250-300 watts with our current workloads. Would you please explain more about the future viability. They are running dual X5670s. We got them cheap but they came with limited ram.

Appreciate your input.

 

[dashoe]

More RAM is better than faster RAM.

Yes, that sound exactly right. In this case I can get to 192GB with 1 chip per channel or with 2 chips per channel at a significant savings. I am curious about the performance difference running at 1333MHz vs 1067MHz at the lower cost. There is also the issue of the larger chips being rank 4 vs rank 2 for the smaller chips and does that have an appreciable effect on performance. Perhaps as @MrGuvernment says, it not worth fussing over.
Thanks for responding

 

[dashoe]

Unless you are running specific apps or services that require superfast memory speed, often to match a processor, you wont notice. For TrueNAS MOARRRRRRRRR is always better

Thank you, guess I won't worry about it.

 

[Ericloewe]

They do run around 250-300 watts with our current workloads. Would you please explain more about the future viability. They are running dual X5670s. We got them cheap but they came with limited ram.

Appreciate your input.

They're at the bare minimum requirements for modern hypervisors, with Westmere Xeons.

 

[joeschmuck]

They're at the bare minimum requirements for modern hypervisors, with Westmere Xeons.

Might be part of the reason they were so cheap, they are about obsolete. Wow, I just did a Google search and they are a really low price. But that means people are flooding the market for a reason.

 

[MrGuvernment]

Thank you, guess I won't worry about it.

Ya, get the fastest supported for your CPU, you want it to match, usually the price difference on older ECC DDR3 ram should not be much (1333MHz vs 1067MHz) If price is that different, shop around just to see.

As noted, the X series were great but they are long in the tooth, and depending what hypervisor your running (ESXi?) they are not supported on newer versions anymore with unsigned drivers.

If this is purely for home lab stuff, meh, who cares, hack it together and make it work, but if it is for work or other more pressing matters, should be looking at newer (but still old) gear.

 

[joeschmuck]

but if it is for work

Purchasing a new server for a business has it's advantages. I would try to get something newer.

If this is purely for home lab stuff, meh, who cares, hack it together and make it work

I couldn't agree more.