Any reason not to buy more RAM?

[guermantes]

Hi,
This is my LAN-only box, see signature, when it's idle, with a few hours distance. I have already ordered another stick of the same 16BG RAM that I've already got, but since swap utilization is almost zero, I was thinking:

-it's primarily a music/non-transcoding video server for one user,
-it holds more RAW photography files that I work on once in a while,
-it runs a Ubuntu server 16.04 in a VM in order to serve LAN-only Nextcloud for one user (contacts and calendar-sync only). The VM is given 2048 MB, just to be sure there is headroom.
-most of the time the freenas is actually just idling along, being an expensive toy

As you can see I am not pushing it in terms of workload. Is the swap well enough to cope with scrubs and activity, or is this a really bad situation to be in? Should I perhaps even turn it off untill the new RAM arrives?

Main reason for this situation: I originally provisioned the RAM to be double my needs of 8GB, but then I decided to buy 6x4 TB HDD, rather than 4x3 TB - and I forgot to recalculate my RAM needs!!

 

[guermantes]

and just as a post that and go back to the admin pages...

 

[MatthewSteinhoff]

If you don't have a performance problem, you're fine. It won't hurt to add more RAM, but I doubt you'll see any benefit. A little bit of swap in use is typically fine. Your operating system is just being efficient and taking something out of RAM that is mostly unused.

The only time I'm really concerned about swap usage is when there are performance problems or if the amount of swap in use grows over time and could indicate a memory leak.

In your case, there doesn't seem to be a performance problem and the amount of swap in use looks constant. I'd skip adding RAM.

Cheers,
Matt

 

[HoneyBadger]

Any reason not to buy more RAM?

The two reasons not to buy more RAM for ZFS are:

1. You're out of available DIMM slots
2. You're out of available money

That said, in your case you likely don't need it as suggested.

If you're running a VM consuming 2048MB of RAM though, I'd suggest reducing your arc_max by that same amount in order to avoid any chance of hitting swap.

 

[guermantes]

Thanks to the both of you! Not really what I expected, but kind of what I was hoping for. I'll look into that arc_max, as well.

 

[adrianwi]

I wish I hadn't hit 1. :D

Not just a case of saving for more memory, but a new board to put it in too. Actually, a whole new system so I can demote the current one to a backup role.

Maybe next year...