The diskcopy command is a diagnostic-level command executed from the ONTAP nodeshell. Its function is to perform a low-level, block-for-block copy of an entire source disk to a destination disk. This process is independent of the file system or RAID layout. It is typically used by support personnel for data recovery efforts on a disk that is showing signs of failure but is still readable, allowing its raw data to be preserved on a healthy spare disk before the original disk fails completely.

A. Pre-failing a drive is a maintenance operation that uses different commands (e.g., storage disk fail) to gracefully remove a disk from an aggregate and initiate a copy to a spare.

C. Copying data to a volume is a logical operation that works at the file system level, not the physical block level of an entire disk.

D. RAID reconstruction is a process managed by the RAID subsystem to rebuild data onto a spare disk after a drive has failed; it is not initiated by the diskcopy command.

1. ONTAP 9 Commands: Manual Page Reference

Reference: The man page for the diskcopy(8) command.

Content: "The diskcopy command copies the contents of one disk to another disk on a block-by-block basis. It is intended to be used to recover data from a failing disk." This directly supports the answer that it performs a low-level copy from one disk to another. (Note: This command is for advanced diagnostic use and its documentation is found within the system's manual pages).

2. NetApp Technical Report TR-4530: Data Recovery Using the diskcopy Command

Reference: Section 1, "Introduction," and Section 3, "Using the diskcopy Command."

Content: The report explicitly states, "The diskcopy command is a diagnostic-level command that can be used to copy the contents of a source disk to a destination disk on a block-by-block basis." This confirms its function as a low-level copy tool for data recovery.