8GB RAM - Drive Size

[NAS-Plus]

I have some Dell PowerEdge 840 tower servers. They have Xeon processors and 8GB of ECC RAM. I understand that the servers will not support over 8GB of RAM. I have 4 x 2TB drives in most of them using RAIDz1 arrays. They work great! I am not doing anything performance intensive. They simply act as a file server or a backup server using Windows SMB shares. I know that the general recommendation is 1 GB RAM per 1 TB drive space, with no less than 8 GB.

How much drive space could I install and still get reliable performance?
4 x 3TB?
4 x 4TB?
4 x 6TB?
4 x 8TB?
4 x 10TB?

What would happen if I exceed the drive space that is able to be supported by the 8GB RAM? Slow write performance, slow read performance, crashes, drive corruption, other?

 

[m0nkey_]

I know that the general recommendation is 1 GB RAM per 1 TB drive space, with no less than 8 GB.

That's not strictly true these days. As long as you have 8GB RAM minimum and not doing anything crazy, you will be fine.

 

[Stux]

The key is to keep an eye on how often it’s swapping.

 

[NAS-Plus]

I'm not sure I know what you mean when you said swapping. Is this the Swap Utilization under Reporting / Memory? Currently the server is showing about 8.0 G Free and almost 0.0 G Used.

 

[NAS-Plus]

Bump

 

[wblock]

Bump

It appeared that your questions were answered. If they weren't, please add enough information to clarify what you are asking.

Summary: if your system is not using a significant amount of swap memory as shown in Swap Utilization under Reporting-->Memory, then more RAM is not needed.

 

[NAS-Plus]

wblock,

Thanks. Can you define a significant amount of swap memory? Would this be 25%, 50%, 75%? So far it looks to be nil (less than 5%).

 

[Ericloewe]

A few MB at a time.

 

[NAS-Plus]

Sorry for my ignorance. Since the Reporting / Memory / Swap Utilization chart is showing about 8.0 G of RAM (8 GB I presume) Free, a few MB would seem to be hardly even noticeable on this chart. Am I missing something?

 

[Ericloewe]

I mean, if it's more than a few MB of swap in use at a time, you have a problem that needs attention.

These small bits of swap are used when memory is needed more quickly than ARC can be cleared to make room for real applications. If you see more than that, there's way too much memory pressure.

 

[NAS-Plus]

Thank you!

 

[wblock]

Under 5%, ignore. If it begins to grow, take notice. The rest is kind of arbitrary, but usually there is a noticeable performance decrease when a machine is low on RAM, and delays as it swaps stuff out to disk.