Hi Steve, On Wed, 11 Mar 2026 at 15:26, Steve Yates <[email protected]> wrote:
> Hi Alwin, > > Thanks for the input. Sounds like "stopped" is the safe way, which is > what I'd assumed. It would be good if that was clarified in the Ceph docs ( > https://docs.ceph.com/en/latest/man/8/rbd/#:~:text=sparsify). > > I found in the Proxmox forum thread that if I create 1+10 GB in two zero > files on a small VM, delete, and trim, "rbd du" USED remained at 37/43 GB > for that VM, so that doesn't help. Also same issue on Windows VMs, and we > have at least one (a pfSense VM) using ZFS, so it's not just EXT4. > AFAIK, in Proxmox VE, QEMU converts zero-writes to discards because "detect-zeroes":"unmap" is set on the disk drives. This suggests that the disks are highly fragmented and the object count doesn't change significantly. A similar thing may apply to ZFS as well. Sparsify discards an object when it consists entirely of zeros, at the object level. But an fstrim might not trim the entire range of an object because it operates at the block level. This potentially leaves empty objects behind, which sparsify will pick up. You could try a storage migration, which might perform a similar function to sparsify and could be done online. > > Re: the serverfault thread, rebooting a VM results in no change in "rbd > du" USED. We do regularly reboot VMs for updates, and migrate too when > rebooting PVE nodes. > Some thoughts about the regular reboot. You've likely thought about this, but eh. :) * Is the discard flag set on the disks? * Is guest-trim enabled for qemu-guest-agent in the VM's options tab after migration/cloning? * Is the "SSD emulation" flag set on the disk tab of the VM? Especially for Windows, as it will switch from defragmentation to TRIM (amongst other things). > > I'm about at the point of ignoring the "rbd du" USED number. It doesn't > seem terribly meaningful. > Yeah, it's an indicator but not really something to worry about unless you're heavily overprovisioning your pools. Cheers, Alwin -- Alwin Antreich Head of Training and Proxmox Services Want to meet: https://calendar.app.google/MuA2isCGnh8xBb657 croit GmbH, Freseniusstr. 31h, 81247 Munich CEO: Martin Verges, Andy Muthmann - VAT-ID: DE310638492 Com. register: Amtsgericht Munich HRB 231263 Web <https://croit.io/> | LinkedIn <http://linkedin.com/company/croit> | Youtube <https://www.youtube.com/channel/UCIJJSKVdcSLGLBtwSFx_epw> | Twitter <https://twitter.com/croit_io> TOP 100 Innovator Award <https://croit.io/blog/croit-receives-top-100-seal> Winner by compamedia Technology Fast50 Award <https://croit.io/blog/deloitte-technology-fast-50-award> Winner by Deloitte _______________________________________________ ceph-users mailing list -- [email protected] To unsubscribe send an email to [email protected]
