OpenStack Block Storage enables you to choose a volume back end according to free_capacity and allocated_capacity. The volume number weigher feature lets the scheduler choose a volume back end based on its volume number in the volume back end. This can provide another means to improve the volume back ends’ I/O balance and the volumes’ I/O performance.
To enable a volume number weigher, set the scheduler_default_weighers to VolumeNumberWeigher flag in the cinder.conf file to define VolumeNumberWeigher as the selected weigher.
To configure VolumeNumberWeigher, use LVMVolumeDriver as the volume driver.
This configuration defines two LVM volume groups: stack-volumes with 10 GB capacity and stack-volumes-1 with 60 GB capacity. This example configuration defines two back ends:
1 2 3 4 5 6 7 8 9 10 11 | scheduler_default_weighers=VolumeNumberWeigher
enabled_backends=lvmdriver-1,lvmdriver-2
[lvmdriver-1]
volume_group=stack-volumes
volume_driver=cinder.volume.drivers.lvm.LVMVolumeDriver
volume_backend_name=LVM
[lvmdriver-2]
volume_group=stack-volumes-1
volume_driver=cinder.volume.drivers.lvm.LVMVolumeDriver
volume_backend_name=LVM
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Define a volume type in Block Storage:
$ cinder type-create lvm
Create an extra specification that links the volume type to a back-end name:
$ cinder type-key lvm set volume_backend_name=LVM
This example creates a lvm volume type with volume_backend_name=LVM as extra specifications.
To create six 1-GB volumes, run the cinder create –volume-type lvm 1 command six times:
$ cinder create --volume-type lvm 1
This command creates three volumes in stack-volumes and three volumes in stack-volumes-1.
List the available volumes:
# lvs
LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert
volume-3814f055-5294-4796-b5e6-1b7816806e5d stack-volumes -wi-a---- 1.00g
volume-72cf5e79-99d2-4d23-b84e-1c35d3a293be stack-volumes -wi-a---- 1.00g
volume-96832554-0273-4e9d-902b-ad421dfb39d1 stack-volumes -wi-a---- 1.00g
volume-169386ef-3d3e-4a90-8439-58ceb46889d9 stack-volumes-1 -wi-a---- 1.00g
volume-460b0bbb-d8a0-4bc3-9882-a129a5fe8652 stack-volumes-1 -wi-a---- 1.00g
volume-9a08413b-0dbc-47c9-afb8-41032ab05a41 stack-volumes-1 -wi-a---- 1.00g
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