32GB RAM but ARC size set automatically to 12.5GB

[Asimov1973]

Hello guys,
Does somebody know if it's possible to increment the ARC Size?
I have 32GB ECC ram, my ARC size is set by the autotuning to 12.5 GB (maybe because when I first installed freenas I had only 16GB of Ram...), my hit Ratio is 94.6%

The Physical Memory utilisation report 13.3 Gb free, 12GB swap used 0Gb

Does somebody have some advices about how I could improve the caching ?

Cheers.

 

[Mirfster]

So when you first enabled Autotune you had 16 GB of RAM correct? Autotune is a one time type thing, it sets those based on the current system specs. If you wanted to reset the settings, you can do see my comments in this thread: Very low ARC Hit Ratio

Some suggest not running Autotune unless you have larger amount of RAM. I have it enabled though even with 32 GB.

 

[SweetAndLow]

Remove all the tuneables that are set and don't bother with auto tune.

 

[DrKK]

Remove all the tuneables that are set and don't bother with auto tune.

What SweetAndLow said is the correct solution.

Wipe the tunables, turn off auto-tune, reboot. Auto-tune is completely inappropriate for a home NAS of any normal size.

 

[Asimov1973]

Hello and thanks everybody for the answers....however I must say that autotune did sensibly increased the performances (expecially CIFS transfer) when I activated it few months ago....why is inappropriate to use them in a hone NAS? could they have a bad effect on something?

 

[Mirfster]

Think that most suggest to NOT use it until to get to 64GB or above of RAM. Which ever works for you IMHO (Since you now know how to disable/undo it if desired).

/I'm sure someone is going to smack me with a mechanical keyboard for saying so... :P

 

[gpsguy]

/we don't need to snack you. The new users can look at your forum title and see who they are talking to. <just kidding>

I appreciate your willingness to help out on the forums.


Sent from my iPhone using Tapatalk

 

[Asimov1973]

Think that most suggest to NOT use it until to get to 64GB or above of RAM. Which ever works for you IMHO (Since you now know how to disable/undo it if desired).

/I'm sure someone is going to smack me with a mechanical keyboard for saying so... :p

Uh...I was speaking about ARC not L2ARC...ARC is in the RAM , L2ARC is your average SSD that you add to your FREENAS once you max out the memory....I guess you got confused.

 

[Mirfster]

Uh...I was speaking about ARC not L2ARC...ARC is in the RAM , L2ARC is your average SSD that you add to your FREENAS once you max out the memory....I guess you got confused.

No confusion, I was speaking about enabling autotune in general. :)

 

[Asimov1973]

Oh...I found my answer :

FreeNAS® provides an autotune script which attempts to optimize the system depending upon the hardware which is installed. For example, if a ZFS volume exists on a system with limited RAM, the autotune script will automatically adjust some ZFS sysctl values in an attempt to minimize ZFS memory starvation issues. It should only be used as a temporary measure on a system that hangs until the underlying hardware issue is addressed by adding more RAM. Autotune will always slow the system down as it caps the ARC.

and:

If you are trying to increase the performance of your FreeNAS® system and suspect that the current hardware may be limiting performance, try enabling autotune.

So basically autotune is for compensating a low quantity of RAM (and not to be activated once we have 64GB...) , moreover autotune will always caps the ARC....so in order to increase my ARC size I need to disable AUTOTUNE.

I will see if performances will increase or decrease and i will keep you guys posted.

Thanks everybody!

 

[Mirfster]

So basically autotune is for compensating a low quantity of RAM (and not to be activated once we have 64GB...)

Pretty much, but actually I think that if you have lots of RAM then autotune may benefit you.

Have a read of this thread: Auto tuning

 

[Robert Trevellyan]

My understanding is that in a small subset of use cases, the system may need to allocate RAM faster than ZFS can relinquish it from ARC usage. In those cases, you need to prevent ZFS from using all your RAM for ARC, and autotune may help with that.

 

[Asimov1973]

Autotune DISABLED, ARC size went to 23.3 GB MAX 20GB min......performances increased of minimum 50% in file transfer and overall reactivity of the system

Autotune did indeed cap ARC size to 12.5 GB...maybe because when I first activated it I had 16Gb of RAM.

With autotune enabled, performances were great, with autotune disabled and 32 Gb of ram, performances are AMAZING!!!
I think I will let AUTOTUNE disabled and enjoy my SuperFast NAS! :)

Thanks all!

 

[Mirfster]

Glad it worked out. Enjoy.