What is a Shadow Store used for in Isilon OneFS?

A.
Shared data for clones and original files

B.
Changed block data for clones and original files

C.
Changed block data for SyncIQ

D.
Changed blocks for SnapshotIQ

Explanation:
http://www.emc.com/collateral/hardware/white-papers/h10588-isilon-data-availabilityprotection-wp.pdf (page 22, see file clones)

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