Hi I need to get some clarification on TRIM handling in KVM virtualmachines on TrueNAS and how the commands are intercepted and passed to ZFS. TrueNAS-SCALE-22.12.0 | Sparse zvol showing considerably higher allocation... Hi all, have been searching for some information on this for a f…

Last I checked, TRIM was not passed through and I also wanted that feature. In theory it’d allow the zvol allocations to be released. And this would then allow the pool trim to trim the released blocks too.

@stux When TRIM is passed through from the VM, ZFS should just tag the relevant blocks as unused in ZFS. “Hardware” TRIM should not be required for this Admins can optionally TRIM their pools. There is a lot of discussion as to whether this is useful for SSD/NVMe and ZFS. Last I checked, TRIM wa…

I thought I felt my ears burning. Reading my old threads, I’m so flustered! discard='unmap' has been in since 24.04.0. To my knowledge this works for both thick and thin provisioned ZVols (though all of my VM ZVols use sparse/thin provisioning so cannot confirm). I don’t think it was backported t…

Is there anyway to know if detect-zeroes has been added? It was added to the road map nearly 2 years ago [image] [MOVED TO ROADMAP] KVM add the `detect-zeroes` feature Feature Requests Problem/Justification This allows ZFS to handle all zero blocks in Virtua…

[image] shoulders: It was added to the road map nearly 2 years ago Oct 2025 is when it was marked as Moved to Roadmap, less than a year ago.

still cannot check though, I don,t have access to the internal issue tracker. :smiley:

KVM and ZVol TRIM/DISCARD passthrough handling clarification

Apps and Virtualization

shoulders September 5, 2026, 8:48am 5

Is there anyway to know if detect-zeroes has been added?

It was added to the road map nearly 2 years ago

Topic		Replies	Views
[MOVED TO ROADMAP] KVM add the `detect-zeroes` feature Feature Requests	1	140	October 3, 2025
Virtual Machines - add detect-zeroes to QEMU startup command Feature Requests	3	44	September 22, 2026
Pool Usage incorrect, can this be fixed? TrueNAS General SCALE	9	210	September 9, 2024
TrueNAS 25.10 “Goldeye” BETA is Available - Blog Post Announcements Goldeye	85	3319	September 18, 2025
Disk Backlog slowing down server TrueNAS General	8	412	May 21, 2024

KVM and ZVol TRIM/DISCARD passthrough handling clarification

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