> I'm confused. How can a 4M discard not free anything? It's either > going to hit an entire object or two adjacent objects, truncating the > tail of one and zeroing the head of another. Using rbd diff: > > $ rbd diff test | grep -A 1 25165824 > 25165824 4194304 data > 29360128 4194304 data > > # a 4M discard at 1M into a RADOS object > $ blkdiscard -o $((25165824 + (1 << 20))) -l $((4 << 20)) /dev/rbd0 > > $ rbd diff test | grep -A 1 25165824 > 25165824 1048576 data > 29360128 4194304 data I have tested this on a small RBD device with such offsets and indeed, the discard works as you describe, Ilya. Looking more into why ESXi's discard is not working. I found this message in kern.log on Ubuntu on creation of the SCST LUN, which shows unmap_alignment 0: Aug 6 22:02:33 e1 kernel: [300378.136765] virt_id 33 (p_iSCSILun_sclun945) Aug 6 22:02:33 e1 kernel: [300378.136782] dev_vdisk: Auto enable thin provisioning for device /dev/rbd/spin1/unmap1t Aug 6 22:02:33 e1 kernel: [300378.136784] unmap_gran 8192, unmap_alignment 0, max_unmap_lba 8192, discard_zeroes_data 1 Aug 6 22:02:33 e1 kernel: [300378.136786] dev_vdisk: Attached SCSI target virtual disk p_iSCSILun_sclun945 (file="/dev/rbd/spin1/unmap1t", fs=409600MB, bs=512, nblocks=838860800, cyln=409600) Aug 6 22:02:33 e1 kernel: [300378.136847] [4682]: scst_alloc_add_tgt_dev:5287:Device p_iSCSILun_sclun945 on SCST lun=32 Aug 6 22:02:33 e1 kernel: [300378.136853] [4682]: scst: scst_alloc_set_UA:12711:Queuing new UA ffff8810251f3a90 (6:29:0, d_sense 0) to tgt_dev ffff88102583ad00 (dev p_iSCSILun_sclun945, initiator copy_manager_sess) even though: root@e1:/sys/block/rbd29# cat discard_alignment 4194304 So somehow the discard_alignment is not making it into the LUN. Could this be the issue? Thanks, Alex Aug 6 22:02:33 e1 kernel: [300378.136782] dev_vdisk: Auto enable thin provisioning for device /dev/rbd/spin1/unmap1t Aug 6 22:02:33 e1 kernel: [300378.136784] unmap_gran 8192, unmap_alignment 0, max_unmap_lba 8192, discard_zeroes_data 1 Aug 6 22:02:33 e1 kernel: [300378.136786] dev_vdisk: Attached SCSI target virtual disk p_iSCSILun_sclun945 (file="/dev/rbd/spin1/unmap1t", fs=409600MB, bs=512, nblocks=838860800, cyln=409600) > > Thanks, > > Ilya _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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