Difference between "Allocated" and "Used" capacities

[feedthemachine]

This is the question I am currently working on and, to my surprise, found it a heavy book. It appeared first, that HPE 3PAR and other vendors do name different things as "Allocated capacity". For instance, here is said that Allocated = Total - Free. Looking to the other non-HP sources, it says that "Allocated capacity is essentially capacity that has been dedicated to host a specific application such as VMWare". 

What's more, even on HPE-related forums and websites I have found many different definitions (which ofc do not correlate with each other):

• Allocated Capacity = Volume + Spare
• Amount of storage remaining for use on the disk drive.
• Allocated capacity is space that is used for chunklets, including chunklets that are used for logical drives, spares, and failed capacity.

Is there an ultimate-defenition of what is "Allocated" space and how does it differ from "Used"?

Thanks in advance!

[yapkl · Accepted solution]

Allocated - means the space you've allocated for host/admin/sparing/failed chunklets/RAID overheards/etc... basically everything that is required to support the management/operations of the 3PAR.

Used - is what is actuallly used to support your host volumes.

You can refer to the SSMC User Guide, e.g. v3.2 here for more details -> https://support.hpe.com/hpsc/doc/public/display?sp4ts.oid=5044394&docLocale=en_US&docId=emr_na-a00021410en_us