The mdadm output shows the array State is clean, degraded, recovering. The degraded and recovering states indicate that the array is operating with a missing device but is actively rebuilding its data onto a replacement. The device /dev/sdf1 has the status spare rebuilding, which confirms that a spare drive has been automatically engaged to replace a failed one (C). This rebuilding process is I/O-intensive, as data must be read from all other active disks to reconstruct the data for the new disk. This overhead significantly impacts both read and write performance, making the overall RAID set performance sub-optimal until the rebuild is complete (B).

A. The array is degraded, recovering, which is not a normal operating status; normal status would be clean without the other flags.

D. The process shown is recovering from a failure, not reshaping to increase the array's size, which is a different operation.

E. Both read and write performance are sub-optimal because reconstructing data for reads from the failed portion and writing parity during the rebuild impacts all I/O.

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1. Oracle® Linux 8: Managing Storage Devices

Chapter 4

"Working with RAID"

Section 4.6 "Monitoring a RAID Device". The documentation explains that the mdadm --detail command displays the array's state. A state including degraded and recovering indicates a rebuild is in progress after a device failure

during which "performance is affected." The presence of a spare rebuilding device confirms a spare has been activated for this purpose.

2. The mdadm(8) Linux manual page. Under the description of array states

recovering is defined as the state where "the array is being rebuilt to recover from a failure." The device state spare rebuilding indicates a spare device is the target of this reconstruction. This process inherently requires heavy I/O

impacting performance.

3. Patterson

D. A.

Gibson

G.

& Katz

R. H. (1988). A case for redundant arrays of inexpensive disks (RAID). SIGMOD '88: Proceedings of the 1988 ACM SIGMOD international conference on Management of data

109–116. This foundational academic paper on RAID explains that during reconstruction (rebuilding)

the array must satisfy user requests while also reading all other disks to reconstruct the lost data

which "degrades performance" (Section 4

Paragraph 3).