Den tors 12 aug. 2021 kl 17:04 skrev Boris Behrens <bb@xxxxxxxxx>: > Hi everybody, > we just stumbled over a problem where the rbd image does not shrink, when > files are removed. > This only happenes when the rbd image is partitioned. > > * We tested it with centos8/ubuntu20.04 with ext4 and a gpt partition table > (/boot and /) > * the kvm device is virtio-scsi-pci with krbd > * Mount option discard is set > * command to create large file: dd if=/dev/zero of=testfile bs=64M > count=1000 > * the image grows in the size we expect > * when we remove the testfile the rbd image stays at the size > * we wen recreate the deleted file with the command the rbd image grows > further Just a small nit on this single point, regardless of if trim/discard works or not: There is no guarantee that writing a file, removing it and then re-writing a file will ever end up in the same spot again. In fact, most modern filesystems will probably make sure to NOT place things at the same spot again. Since the second write ends up in a different place, it will once again expand your sparse/thin image by the amount of written bytes, this is very much to be expected. I'm sorry if you already knew this and I am just stating the obvious to you, but your text came over as if you expected the second write to not increase the image since that "space" was already blown up on the first write. Trim/discard should still be investigated so you can make it shrink back again somehow, just wanted to point this out for the records. -- May the most significant bit of your life be positive. _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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