ARC and memory cache

[IBCMED]

What is the "ARC" you guys talk so much about? I have a problem with cached memory on my TrueNAS, whenever ZFS stores it allocates a lot of memory, the system is slow, almost crashing. I checked in several threads that touch this word "ARC". Can you explain to me why and what it is?

 

[Patrick M. Hausen]

It's the Adaptive Replacement Cache. The memory in which ZFS caches things. How much RAM does your system have? How large is your ZFS pool? How large is the workload you are reading and writing when the system is slow?

Please start with describing your hardware and configuration and TrueNAS version. Thank you.

 

[IBCMED]

Ok, thanks! My system contains:

CPU: Intel Core i3 8100 3.6GHz
RAM: 64GB
Version of TrueNAS: 12.0-U8.1
Pool size: 24.54 TiB Total - 16.64 TiB (68%) Used

About the workload, I just check that the processor heats up and gets above 50% usage along with ZFS allocating most of the memory at the same time, I don't know if that explains something.

 

[Patrick M. Hausen]

Are you using dedup or any compression apart from the default LZ4?

 

[IBCMED]

Are you using dedup or any compression apart from the default LZ4?

I've heard about this dedup but never used it, what would it be? I don't know how to answer this question exactly friend, as I'm new to TrueNAS and I still don't know half of its features, sorry

 

[Patrick M. Hausen]

I was just trying to find out if you were using specific options that are known to be extremely memory and/or CPU hungry. Seems like you don't.

 

[IBCMED]

Oh yes yes, I don't believe so friend, I'm using the system for my company, just to manage access and share folders even hehe. Do you have any other ideas of what it could be? Thanks in advance for getting in touch!

 

[Patrick M. Hausen]

I already answered in that other thread you created. Please do not open multiple threads for the same topic.

 

[IBCMED]

Yes sir, I just wanted to give more details that I noticed about the events, so I opened another one. Forgive me.