SOLVED Does adding more RAM to a FreeNAS server improve stability/performance?

[Muku]

I have supermicro X10SLM-F in my FreeNAS server along with crucial 16GB (8x2) RAM. Currently I'm using 6 x 2TB WD Red in Raid Z2. My system is running fine as of now.

I'm planning to throw out 2TB HDDs in future & fill them with higher capacity HDDs.

So, does adding another 16GB (8x2) of same make & model RAM kit improving my performance/stability? I'll only add them if it is absolutely necessary as I don't get them anywhere in my country. I've to import them from USA.

Thanks in advance

 

[Jailer]

16GB is usually enough for a home user. If your performance and stability is good now it will likely be good after the drive upgrade. If you find that it's not then get the extra memory.

 

[Muku]

I've absolutely no issues with my current setup but I think I've read somewhere that you need to have larger RAM if you want to have high capacity HDDs in FreeNAS. That's why I'm concerned. Do you have any idea how big of a HDD can 16 GB RAM handle? Is there any such limit? For example can I add 6 x 8TB WD Red with just 16GB of RAM?

 

[Jailer]

It depends entirely upon your usage. If you have a lot of user, jails or vm’s then the extra memory would be beneficial. If it’s just serving up files you’ll likely be just fine.

 

[Chris Moore]

I've absolutely no issues with my current setup but I think I've read somewhere that you need to have larger RAM if you want to have high capacity HDDs in freenas. That's why I'm concerned. Do you have any idea how big of a HDD can 16 GB RAM handle? Is there any such limit? For example can I add 6 x 8TB WD Red with just 16GB of RAM?

The answer @Jailer gave you is absolutely accurate. I run a server at work that has 60x 6TB drives and it runs just fine with only 32GB of memory. The additional RAM would be used for Adaptive Replacement Cache (ARC) which can make the system perform better but only under certain circumstances where your users repeatedly access the same data within a certain amount of time. You can look at your "ARC Hit Ratio" in the reporting pages of your web GUI and get an idea how much it is being used. I have another system with 16GB of memory and it is using 11.8 GB of memory for ARC and has a 75% ARC Hit Ratio. The system with 32GB of memory is currently only using 8.6 GB of memory for ARC and has a 63% ARC Hit Ratio. So, it depends entirely on the type of work the system is doing. Even with more memory, it is not guaranteed to help performance.
If you are running some Jails or Virtual Machines (VMs) it would be a good thing to have more memory to ensure there are plenty of resources to go around.
After you install the new drives, you can monitor the performance in the Reporting tab and decide if you need more memory. Not having it will not prevent the system from running as long as you have met the minimum requirement. The old "rule of thumb" about having 1GB of RAM for every 1TB of storage was a guideline to keep people from trying to run a system with 21TB of storage and only 2 or 4 GB of memory. Those configurations could not work properly because they didn't have enough memory for ARC and for the operating system.

 

[Muku]

Thanks a lot guys. So, I'm sticking to 16 GB of RAM for now.

 

[Muku]

The answer @Jailer gave you is absolutely accurate. ........ You can look at your "ARC Hit Ratio" in the reporting pages of your web GUI and get an idea how much it is being used......

Can you please tell me how to check for ARC Hit Ratio?

 

[Chris Moore]

Just click the Reporting button in the top menu, then click the ZFS button in the sub-menu, then look at the charts.
Look at this.

 

[Muku]

Just click the Reporting button in the top menu, then click the ZFS button in the sub-menu, then look at the charts.
Look at this. View attachment 21443

Hello @chris, my reporting page looks like this


Can u explain what does the charts say? Does the system actively using only 10 GB of RAM out of 16? And why is my ARC hit ration so high? I just use my Freenas as a home file server with occasional uses with hardly 1-2 user accessing it simultaneously.

 

[Bidule0hm]

Does the system actively using only 10 GB of RAM out of 16?

Yes, but it's only the ARC, the rest of the system can use the other 5-6 GB.

And why is my ARC hit ration so high?

That's normal. The higher the better. It show you get most of the data from the cache (ARC) and not the pool so it's faster.