[PVE-User] Force reclaiming space on a vdisk...

[Daniel Plominski]

Hello,

we have had very bad experience with trim, due to a virtio driver error, 
a special release, the trim resulted in a corrupt Windows NTFS file 
system.

The bug is fixed in the latest stable VirtIO drivers, but we only use 
the legacy method using targeted "dd" (zero) cleanup on Linux / BSD VMs 
and on Windows using "fsutil".

>From the perspective of the HOST system, a zvolume formatted with 
filesystem and stored data is simply a "data container" with 
unstructured data (depending on the structure, however, this can be 
compressed well).
If now within the VM an area with zeros is written, this zvolume area is 
stimulated to overwrite the contained data, the process is compressed 
and the occupied blocks are released.

The block free up should also work with the ZFS algorithm "zle".

How often the cells of an SSD / NVME memory are overwritten depends on 
the internal intelligence of the firmware / controller of the respective 
memory.

TRIM "Discard" (if supported by the hardware, the hypervisor, the 
hypervisor driver and the guest OS) can be used to better control this 
remapping.

ASS - Der Bildungseinrichter GmbH
Mit freundlichen Grüßen

DANIEL PLOMINSKI
Leitung IT | Head of IT

Telefon 09265 808-151 | Mobil 0151 58026316 | dpl at ass.de
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