Question on Ram Consumption

[cshill]

I am noticing that a lot of ram is being consumed by one of my machines, but in actuality I am not sure what is consuming it. I used shell to get into the server and ran htop and here are the results.


However, the gui is telling me that I'm near maxed out.

I have only two machines that are running and the htop command lists one of them on the right, my Windows11 machine. So the htop command is showing me all the memory consumed on the machine including the VMs.

I do know that I'm extensively testing the replication and HA functions and I know that constantly having my servers communicate and update each others storage will consume ram but shouldn't that be listed as well?

What are the requirements/general guidelines around ram consumption? I read that about 8GB should be reserved for my ZFSpool but not sure how much is supposed to be consumed for a 2TB HDD. How much for 5 disks but at 250GB? Is it based solely on the amount of disks or does the size of the disk matter too?

 

[BobhWasatch]

The yellow color in htop is cache. If you are doing a lot of moving of files then it is normal that cache goes up.

https://serverfault.com/questions/180711/what-exactly-do-the-colors-in-htop-status-bars-mean

 

[cshill]

But doesn't the cache still count towards the overall amount of ram consumed? Looks like it doesn't.

 

[leesteken]

But doesn't the cache still count towards the overall amount of ram consumed? Looks like it doesn't.

Some software counts it as used, other software counts it as free. Windows users think free memory is important, Unix users think of free memory as wasted memory. There is someone confused about this every week. Please search filesystem cache for more examples on this forum about this.

EDIT: This might also be relevant since you use ZFS: https://pve.proxmox.com/pve-docs/pve-admin-guide.html#sysadmin_zfs_limit_memory_usage

 

[BobhWasatch]

What @leesteken said. Cache is backed by a file so the kernel can just grab some of it when it needs memory. All that means is that something may need to be read from disk on down the road.

 

[cshill]

I found this piece of information in the documentation. It looks like ZFS is a ram muncher. Effective system but the larger we go the more it eats. I don't have enough storage to test but to see if it actually maxes at 16GB.

3.9.8. Limit ZFS Memory Usage​

ZFS uses 50 % of the host memory for the Adaptive Replacement Cache (ARC) by default. For new installations starting with Proxmox VE 8.1, the ARC usage limit will be set to 10 % of the installed physical memory, clamped to a maximum of 16 GiB. This value is written to /etc/modprobe.d/zfs.conf.
Allocating enough memory for the ARC is crucial for IO performance, so reduce it with caution. As a general rule of thumb, allocate at least 2 GiB Base + 1 GiB/TiB-Storage. For example, if you have a pool with 8 TiB of available storage space then you should use 10 GiB of memory for the ARC.
ZFS also enforces a minimum value of 64 MiB.