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Config Guide
With the introduction of the term disk group, RealStor will provide a new set of CLI commands to configure disk
groups: add disk-group, remove disk-groups, show disk-groups, etc. Disk groups are a group of disks that
together form a RAID set.
In a V2 (RAIDar 2.0) environment, disk groups are exactly the same as vdisks. Commands used to manage vdisks in
GL105 code will be the same as in the V2 interface.
With volumes now residing in pools, a new set of CLI commands is available to manage them; show pool, remove
pool, etc.
As highlighted above, the CLI will allow supporting for host groups in both the V2 and V3 interface modes.
However, the term host can have a different meaning depending on whether you are grouping, or using the legacy
context of the command. RealStor will also introduce volume groups for virtual volumes. For additional
information regarding CLI command changes, please refer to the CLI Reference Guide for a more detailed description.
8.4. RealThin: Thin Provisioning
Thin Provisioning allows storage allocation of physical storage resources only once they are consumed by an
application. Thin Provisioning also allows over-provisioning of physical storage pool resources allowing ease of
growth for volumes without predicting storage capacity upfront. Thin Provisioning is available with GL200 firmware
or newer.
Thin Provisioning and Modern File Systems
Many modern operating systems become automatically aware of an array's ability to support thin provisioning. This is
true of Windows 2012 / 2012 R2 and Linux with newer 6.x kernels. When using a non-thin provisioned storage array
the deletion of a file does nothing more than rearrange the file system pointers.
If the array supports thin provisioning, as with RealStor, thin-aware operating systems will notify the storage array to
free the storage that had been allocated to the file that was deleted. This happens with the SCSI UNMAP command.
This will allow for the re-use of the capacity that had been allocated for the deleted file.
Windows 2012 / 2012 R2 also issues notifications when the allocations reach a high percentage of the "advertised"
capacity. This, along with the capacity usage notifications, signals the user that it may be time to add more physical
storage.
How Do I Enable Storage Over-Commitment With RealStor?
Overcommit is a pool setting (default on). When enabled, the aggregate capacity of a volume can exceed the physical
backing storage.
The user can create a volume on a pool with over-commitment Enabled. No configuration needs to be done to create
such a volume. Figure 3 shows that a volume can be logically larger than the pool that it's assigned to.
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Figure 3 – Volume that is logically larger than the pool
AssuredSAN 3xx4
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