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8 Dell PS Series Arrays: Advanced Storage Features in VMware vSphere | TR1066
To calculate the percentage of deleted blocks to be reclaimed, it is necessary to know the amount of free
space on the datastore as seen from vCenter, and the amount of free space in the volume as seen on the
array interface.
π‘£πΆπ‘’π‘›π‘‘π‘’π‘Ÿ π‘‘π‘Žπ‘‘π‘Žπ‘ π‘‘π‘œπ‘Ÿπ‘’ π‘“π‘Ÿπ‘’π‘’ π‘ π‘π‘Žπ‘π‘’ βˆ’ π‘Žπ‘Ÿπ‘Ÿπ‘Žπ‘¦ π‘£π‘œπ‘™π‘’π‘šπ‘’ π‘“π‘Ÿπ‘’π‘’ π‘ π‘π‘Žπ‘π‘’
π‘£πΆπ‘’π‘›π‘‘π‘’π‘Ÿ π‘‘π‘Žπ‘‘π‘Žπ‘ π‘‘π‘œπ‘Ÿπ‘’ π‘“π‘Ÿπ‘’π‘’ π‘ π‘π‘Žπ‘π‘’
βˆ— 100
In an example with a 1000GB thinly provisioned volume, the array shows 200GB free and vCenter shows
the datastore as having 300GB free.
300𝐺𝐡 βˆ’ 200𝐺𝐡
300𝐺𝐡
βˆ— 100 =
100𝐺𝐡
300𝐺𝐡
βˆ— 100 = 33.33%
2.5.2 Space reclamation process on vSphere 5.5
With the release of vSphere 5.5, VMware changed the command for performing the unmap operation and
the behavior of the unmap command. The command is now a part of the existing esxcli command set,
which enables the command to be accessed from many scripting tools and to be called remotely with
vSphere vMA or vCLI. In addition to this new capability, vSphere administrators can specify which datastore
to unmap and can use the operation to unmap the entire datastore, making it easier to keep thinly
provisioned datastores thin.
The full syntax of the command is:
esxcli –server=server_name storage vmfs unmap –-volume-label=volume_label | --
volume-uuid=volume_uuid [--reclaim-unit=number]
To specify the datastore to be unmapped, use either --volume-label or --volume-uuid. The optional
parameter, --reclaim-unit, has a default value of 200 units and specifies the size of the temporary
balloon file that is created per iteration with a default of 200 1MB blocks. VMware will continue to create
temporary balloon files of the specified size until it has reached the end of the datastore. Dell
recommends using the default value for the --reclaim-unit command.
Note: VAAI thin provisioning space reclamation requires Dell PS Series firmware 6.0 or above.