FTP transfer fills system memory buffer

  • Dear all,

    I installed a fresh (newest version) of OMV inside of a VM on proxmox. OMV has direct access to two disks and is installed on a small virtual block from another disk. All disks are directsync (default no cache). The directly connected disks are in a RAID 1 array inside of OMV.


    When I connect to the OMV VM with a FTP connection and transfer files from my PC to OMV the RAM (system) slowly starts to fill up. I base this on the proxmox web UI and the results of "top" inside the VM shell.


    The buffer stays there, no change. Even after multiple days (!) with no further activity on the OMV VM the buffer stays filled.


    As a first attempt I tried to set the all the disks of OMV to directsync inside of proxmox. This disables write cache. This first attempt did not have any effect. My suspicion is that the "problem" is inside of the VM. Not even specific to OMV, but maybe related to some FTP setting?


    Reason: I understand that buffering is normal behavior, in case that another program needs a bit of RAM it will decrease the buffering to accommodate the new program. Though, in my current setup I over-provision my RAM in proxmox to facilitate a sudden burst of RAM usage from time to time. With openmediavault buffering the whole RAM its assigned also the over-provisioned part is used. Not to mention that in normal usage its far below normal RAM usage, thus leaving more RAM for another VM.


    Goal: I understand some caching/buffering can even be beneficial for the stability or safety for writing data. Though, the fact that it stays there is not desirable. What setting do I need to change in order to change this behavior?


    A lot people are reading the post, but not responding. Is something unclear here?

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