Is there a such thing as too much RAM?

[Marlberg]

I currently have 64GB of Registered DDR3 ECC (8x8gb) on my FreeNAS 11.3 build I have 128GB of the same RAM in transit (16x8gb) for a total of 192GB of RAM. Is there a point at which more RAM (either in population of sticks or in density of sticks) becomes less advantageous to a FreeNAS server? The board and cpu's support up to 768GB of ECC RAM (2 cpu x 384GB per CPU) but I am not sure that 3/4 TiB of RAM is even useful outside of many vm's running simultaneously?

 

[PhiloEpisteme]

FreeNAS is ram hungry because of the ARC. The ARC improves your read performance when there is an ARC hit. More ram will not typically hurt your system; but it might not help either. If you're seeing a near 100% ARC hit ratio with your current ARC size; increasing its size will not have an appreciable affect on your performance.

L2ARC on the other hand CAN negatively impact performance because the L2ARC must have its index store in ram; thus consuming ARC space. As a general rule of thumb; don't add an L2ARC device until your ram is maxed out and you're seeing a lower-than-desired ARC hit ratio.

 

[HoneyBadger]

Maybe if you have more RAM than actual raw storage, it's "too much" - but other than that, no. Ideally you would try to have enough RAM to fit your entire working set of frequently accessed data into the ARC to offer extremely fast response, but that's often impractical from a cost perspective.

What is the workload being serviced by the FreeNAS server?

 

[Marlberg]

Thank you! Yes I knew it was RAM intensive due to the ARC being handled on the RAM but just wondering if there is a "break even" point on RAM where adding more buys you less performance per unit cost.

 

[Dan Tudora]

Thank you! Yes I knew it was RAM intensive due to the ARC being handled on the RAM but just wondering if there is a "break even" point on RAM where adding more buys you less performance per unit cost.

hello
but IF YOU read what say Bill Gates when launch DOS (640 KB is enough for ALL operation) is a LEGEND
RAM is not enough never
is a problem of costs. IF you do not need never don't buy !!
adjust your system for yous need !!
and something extra
not extra kill
but no more
add RAM in future if need

succes

 

[PhiloEpisteme]

Thank you! Yes I knew it was RAM intensive due to the ARC being handled on the RAM but just wondering if there is a "break even" point on RAM where adding more buys you less performance per unit cost.

The performance gain per cost will entirely depend on how you use your system. If you 1 user infrequently using the system you'll be much happier with less ram. If you have several users accessing the system many times throughout the day you would benefit from more. The judge on whether to buy more ram or not can be made in part by looking at your ARC hit ratio.