[SOLVED] Trim/discard With CEPH Rbd

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paulohnk1

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May 22, 2020
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Hello

I realized that I'm deleting data from the vms but this space is not being released in Ceph. I found in the documentation that I should do a Fstrim in the RDB but I can't find its assembly text such as: fstrim /mnt/ myrbd.

Any idea?

Thank you
 
paulohnk1 said:
I realized that I'm deleting data from the vms but this space is not being released in Ceph. I found in the documentation that I should do a Fstrim in the RDB but I can't find its assembly text such as: fstrim /mnt/ myrbd.
Click to expand...
man fstrim
And the VM needs to have VirtIO SCSI as its disk controller.
 

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paulohnk1 said:
the vms already have the VirtIO SCSI driver and also fstrim was executed
Click to expand...
Is the discard checkbox ticked on that disk?

paulohnk1 said:
fstrim is executed on the RBD itself and on Proxmox I can't see where the RDB is mounted.
Click to expand...
It will not be and it doesn't need to be. Qemu uses librbd to talk with Ceph directly.
 
I will reproduce the steps that worked for me:

rbd feature disable reply_3/vm-112-disk-0 object-map fast-diff deep-flatten

rbd map reply_3/vm-112-disk-0

rbd showmapped: 0 reply_3 vm-115-disk-0 - /dev /rbd0

mount /dev/rbd0 /mnt

fstrim -v /mnt

Now I can see the space released in Cephs :)

Thanks
 
Hi

I've been searching aswell as we are playing with ceph with some test servers atm but found the same issue with an external source on rook-ceph which sais some options need to be enabled:

https://github.com/rook/rook/issues/6964

bdev_async_discard and bdev_enable_discard on the osds themselves

not sure if this could be it?
 
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