How can I take advantage of more RAM?

[tucansam]

I am running 4GB in each of two bone-stock plain-vanilla unraid servers (v6).  No virtualizations, no extras like sab or sickbeard etc.  Just unraid.

 

I've read that certain kernel parameters can be tweaked to take advantage of more memory for things like writes, caching, etc.  I do not use cache drives in either system anymore, and have noticed a little drop in performance on writes (as to be expected).

 

I also had my primary unraid server completely stop responding to SMB traffic during a parity check.  I could telnet in, but sysload was over 7.0 and all RAM was in use.

 

I have some extra RAM laying around from various builds.... I can put 8GB in one and 12GB in the other.

 

Wondering what kernel tweaks to make to take advantage of the extra memory, seems a waste to have this RAM just sitting in a drawer somewhere, if I can get a little performance bump out of it.

 

Thanks.

[jonp]

Nope, Linux is smart enough to take advantage of all the RAM available on your system. Nothing you need to do to make it take advantage of it.

[tucansam]

Thank you, I appreciate it.

 

Since this RAM is just laying around, I'm going to install it.  But what should my expectations be, realistically?  Going from 4-8GB RAM on a 15TB array and 4-12GB RAM on a 40TB array... I'm not expecting to have my socks knocked off, but will I likely see any faster response times in terms of writing to, reading from, accessing shares, etc?  Or will be benefit be essentially imperceivable?

 

Thanks again.

[jonp]

Think of RAM as a mini version of a cache disk.  Writes to the system first commit to RAM before being flushed to disk.  If the size of the write operation is < the amount of free RAM available, the operation will most likely max out your network transfer speed (~100 MB/s) for the transfer. However, if you started another transfer immediately after the first ended and the previous transfer hadn't flushed to disk yet, then your transfer rate for the second copy would slow down.

 

The biggest true benefit of additional memory on a system (IMHO) is your ability to support more apps and VMs.  If you want to improve write performance, a cache drive/pool is a better way to spend money.  In your case, if the RAM is lying around, sure, throw it in, but don't expect much in terms of an improvement to basic NAS functionality.