[SOLVED] RAM usage in proxmox

[ahmedelemam]

I have a proxmox node that is reporting the used ram way higher than the summed assigned ram of the working VMS



the above is reporting around 116G of ram used, but I only have the following VMs running








if we took the sum of all reported VMS RAM usage, it will account to 36G and the sum of the assigned RAM will be 52G which is less than half of the reported used memory by the node
i'm quite new to proxmox, is there some optimisation that i should do to make this better

 

[Neobin]

Can you please provide the output in code-tags of:

• arc_summary -s arc
• free -h

 

[ahmedelemam]

HYG

root@pve0:~# arc_summary -s arc

------------------------------------------------------------------------
ZFS Subsystem Report                            Thu Sep 01 17:14:21 2022
Linux 5.15.39-4-pve                                           2.1.5-pve1
Machine: pve0 (x86_64)                                        2.1.5-pve1

ARC status:                                                      HEALTHY
        Memory throttle count:                                         0

ARC size (current):                                    56.9 %   71.6 GiB
        Target size (adaptive):                        57.4 %   72.3 GiB
        Min size (hard limit):                          6.2 %    7.9 GiB
        Max size (high water):                           16:1  125.9 GiB
        Most Frequently Used (MFU) cache size:         78.5 %   53.5 GiB
        Most Recently Used (MRU) cache size:           21.5 %   14.6 GiB
        Metadata cache size (hard limit):              75.0 %   94.4 GiB
        Metadata cache size (current):                  4.5 %    4.2 GiB
        Dnode cache size (hard limit):                 10.0 %    9.4 GiB
        Dnode cache size (current):                   < 0.1 %    2.3 MiB

ARC hash breakdown:
        Elements max:                                              11.3M
        Elements current:                             100.0 %      11.3M
        Collisions:                                                10.1M
        Chain max:                                                     7
        Chains:                                                     1.5M

ARC misc:
        Deleted:                                                      56
        Mutex misses:                                                  0
        Eviction skips:                                               19
        Eviction skips due to L2 writes:                               0
        L2 cached evictions:                                     0 Bytes
        L2 eligible evictions:                                 962.5 KiB
        L2 eligible MFU evictions:                      5.0 %   48.0 KiB
        L2 eligible MRU evictions:                     95.0 %  914.5 KiB
        L2 ineligible evictions:                                16.0 KiB

root@pve0:~# free -h
               total        used        free      shared  buff/cache   available
Mem:           251Gi       118Gi       131Gi        68Mi       1.7Gi       131Gi
Swap:          8.0Gi          0B       8.0Gi
root@pve0:~#

 

[Neobin]

ARC size (current): 56.9 % 71.6 GiB

There is your "missing" memory.

It is ZFS's Adaptive Replacement Cache [1] and can be freed, if the system/other processes need the memory.
You can also limit its size [2] [3].

[1] https://www.45drives.com/community/articles/zfs-caching
[2] https://pve.proxmox.com/wiki/ZFS_on_Linux#sysadmin_zfs_limit_memory_usage
[3] https://pve.proxmox.com/wiki/ZFS:_Tips_and_Tricks#Install_on_a_high_performance_system

 

[ahmedelemam]

Thanks for the info, much appreciated

 

[Matthias.]

Great! Please mark the thread as solved (edit it, there's a dropdown near the title) so others with the same problem can find it more easily.