Memory usage by Freenas

[flyinfitz1]

Ive noticed that memory doesnt ever return to "free" unless I reboot the system. See attached image. Is this normal? It seems all the memory is being used within a matter of hours after reboot as well. Faster if Im using the services like plex or SMB frequently.

SPECS:
Lenovo TS140
FreeNAS-9.3-STABLE-201509160044
PlatformIntel(R) Core(TM) i3-4130 CPU @ 3.40GHz
Memory 12 GB ECC
HDD: 4x3TB RAID-Z2 Western Digital Red

 

[danb35]

Perfectly normal. FreeNAS, like most modern and intelligent operating systems, will consume all (or almost all) the RAM you give it, for caching if nothing else. Since FreeNAS uses ZFS, there's a lot of caching going on.

 

[HoneyBadger]

Why would you want perfectly useful RAM to sit idle? Free RAM is wasted RAM. Either a jail will consume it for its own needs, or it will get given to ZFS for ARC.

 

[flyinfitz1]

Thanks everyone, I guess Im stuck in the Windows world where completely used RAM can cause adverse performance of the system.

 

[Ericloewe]

Thanks everyone, I guess Im stuck in the Windows world where completely used RAM can cause adverse performance of the system.

Same as any OS...

And like any modern OS, Windows will cache frequently-used files in unused RAM and FreeNAS will hand over unused RAM to ZFS, which will cache stuff in ARC.
Do not mistake "unused" with "unavailable". If it comes to that, ARC can be reclaimed for other processes.

 

[NAStard]

Hello,

Are the RAM requirements for FreeNAS dropping?
Perhaps on the latest release?
FreeBSD freenas.local 9.3-RELEASE-p28

On my system, I recall that the memory graphs
in the Reports section of the GUI indicated that
memory was always nearly maxed out or perhaps
memory was never returned after being allocated.
But now it appears I have plenty of free memory,
like 6GB. And that's awesome! :)

I wonder what changed? The FreeBSD platform
or the reporting tools?

:D

 

[anodos]

Hello,

Are the RAM requirements for FreeNAS dropping?
Perhaps on the latest release?
FreeBSD freenas.local 9.3-RELEASE-p28

On my system, I recall that the memory graphs
in the Reports section of the GUI indicated that
memory was always nearly maxed out or perhaps
memory was never returned after being allocated.
But now it appears I have plenty of free memory,
like 6GB. And that's awesome! :)

I wonder what changed? The FreeBSD platform
or the reporting tools?

:D

Or the amount you're using the NAS after the last reboot / time since last reboot. If you want lots of free ram, reboot all the things. Often. :D

 

[Ericloewe]

Hello,

Are the RAM requirements for FreeNAS dropping?
Perhaps on the latest release?
FreeBSD freenas.local 9.3-RELEASE-p28

On my system, I recall that the memory graphs
in the Reports section of the GUI indicated that
memory was always nearly maxed out or perhaps
memory was never returned after being allocated.
But now it appears I have plenty of free memory,
like 6GB. And that's awesome! :)

I wonder what changed? The FreeBSD platform
or the reporting tools?

:D

In a word? No.

 

[devnullius]

I understand: "use all RAM available"...

But when there's nothing to do, no IO, no nothing I can think off... I feel it is strange to keep that 'old' data persistently in RAM. Nothing wrong with releasing RAM even if you have plenty to spare, no? :)

 

[Ericloewe]

I understand: "use all RAM available"...

But when there's nothing to do, no IO, no nothing I can think off... I feel it is strange to keep that 'old' data persistently in RAM. Nothing wrong with releasing RAM even if you have plenty to spare, no? :)

It's released as soon as ZFS thinks something would benefit more from being in RAM.

 

[DrKK]

It's released as soon as ZFS thinks something would benefit more from being in RAM.

Indeed.

As you read from your pool, the blocks you are reading become part of your ARC, which has a number of subparts, include a "most recently used" MRU, and a "most frequently used" MFU cache. It will consume as much RAM as appears to be freely available for those tasks, minus about 1GB typically. The nice thing is that the ARC cache is wholly dispensible; when a process requests a large amount of RAM that isn't available, FreeNAS (rather, ZFS) will, as needed, relinquish the least useful parts of whatever it has in the ARC, so that no one is starved for required RAM.

It's perfectly normal, cuspy, behavior, sir.

 

[devnullius]

M'am :) Ok, thanks for the feedback. On the end of the day, it feels 'bad' to me, not releasing RAM. But I understand what they are doing :)

 

[danb35]

You paid for the RAM. Shouldn't the system use it for something?

 

[jgreco]

It's released as soon as ZFS thinks something would benefit more from being in RAM.

Or as soon as ZFS is *sure* that the data has no further value, such as when you free a block on the pool (think: file deletion, etc).

The classical example is to read a file that is a substantial portion of your ARC repeatedly, until it is clearly cached in ARC, and then delete the file. Suddenly your ARC size will plummet.

There is absolutely no value to freeing RAM just to have "more" "free" RAM. That's just kinda a geek-handwringing thing and ZFS will actually use as much ARC as you give it (up to the size of the stored/accessed data on the pool).

 

[devnullius]

"Or as soon as ZFS is *sure* that the data has no further value, such as when you free a block on the pool (think: file deletion, etc)." - that makes me breath normally again :)

"You paid for the RAM. Shouldn't the system use it for something?" - so you keep your brand new Mercedes running 24/7? ;-)

 

[danb35]

"You paid for the RAM. Shouldn't the system use it for something?" - so you keep your brand new Mercedes running 24/7? ;-)

Does having data in your RAM cause any more wear than not having data in the RAM? If so, your question is relevant. If not, however, this is a red herring.

 

[Ericloewe]

"Or as soon as ZFS is *sure* that the data has no further value, such as when you free a block on the pool (think: file deletion, etc)." - that makes me breath normally again :)

"You paid for the RAM. Shouldn't the system use it for something?" - so you keep your brand new Mercedes running 24/7? ;-)

You do, if you're a taxi company.

 

[devnullius]

You do, if you're a taxi company.

Yeah, I'm always annoyed by them too! XD

 

[jgreco]

Yeah, I'm always annoyed by them too! XD

Isn't there that new data taxi service... what is it... oh yeah, Zber.

 

[Ericloewe]

Isn't there that new data taxi service... what is it... oh yeah, Zber.

I see what you did there.