How Much ARC RAM To Assign?

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Stereoscope

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I want to set up a workstation with Proxmox rather than triple boot with Ubuntu, Windows and Proxmox Backup Server. I will use one VM at a time and I want to allocate as much RAM to the active VM as possible. Question is, how much ARC RAM should I assign to Proxmox? I want to give it as little RAM as possible. Is 2GB feasible? I'm not 100% sure what the ARC RAM in the case of Proxmox is even used for?
 
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That depends on a lot of things. I personally use a max of 2G for some systems too. As long as your performance is acceptable and your hit ratios and such in zarcsummary look good this should be okay.
 
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Why do you want to use ProxmoxVE for this? Ubuntu with virtualbox, virt-manager or incus/lxd would propably be a better fit.

For zfs following writeup by @chrcoluk should answer your questions:
C

Thread 'ZFS ARC compared to linux page cache.'

Hi guys, I have decided to make this thread as there is threads popping up related to the ARC.

In my experience ZFS ARC is a lot more polite than the old 'host page cache', and is also actually much more configurable. However its defaults are not necessarily suited for proxmox due to that ARC usage isnt considered as available by the linux kernel.

If you use ext4 on the host, then the page cache will be used by the operating system, this cache can consume almost all of your free ram, has a dumb eviction mechanism, is barely configurable, and if swap file is enabled will usually...
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Impact said:
That depends on a lot of things. I personally use a max of 2G for some systems too. As long as your performance is acceptable and your hit ratios and such in zarcsummary look good this should be okay.
Click to expand...
Looking into zarcsummary thanks.
Johannes S said:
Why do you want to use ProxmoxVE for this? Ubuntu with virtualbox, virt-manager or incus/lxd would propably be a better fit.
Click to expand...
I suspect your suggestion is to use Ubuntu as a base system like Proxmox is in my current plan? So Ubuntu will have native performance but Windows and PBS will run in a VM either through VirtualBox or virt-manager?
The problems I see with this are:
- I can't pass the GPU to Windows because it's used by Ubuntu and I want to be able to use the GPU natively in Windows.
- All the drives used by PBS are visible in Ubuntu upon boot. I want only PBS to ever see the drives. A workstation seeing the drives of PBS is not something I want. If I use Proxmox, I can assign which VMs get the spinning rust passed through i.e. PBS and then Windows and Ubuntu VMs never know that they exist.
Johannes S said:
C

Thread 'ZFS ARC compared to linux page cache.'

Hi guys, I have decided to make this thread as there is threads popping up related to the ARC.

In my experience ZFS ARC is a lot more polite than the old 'host page cache', and is also actually much more configurable. However its defaults are not necessarily suited for proxmox due to that ARC usage isnt considered as available by the linux kernel.

If you use ext4 on the host, then the page cache will be used by the operating system, this cache can consume almost all of your free ram, has a dumb eviction mechanism, is barely configurable, and if swap file is enabled will usually...
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Click to expand...
Thanks for the link. Not clicking yet, but I'll come back and re-read a few times as I learn a bit more about this.
 
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