What is an 'UNC' error?

• A. Uncorrectable write error — cannot write data.
• B. Uncorrectable read error — drive could not recover data.
• C. Undefined data collection status.
• D. Unit not connected.

Answer: (B)

UNC stands for an uncorrectable read error. When a disk tries to read a sector, it uses error-correcting code and may retry several times. If the data cannot be reconstructed despite those efforts, the drive reports an uncorrectable read error, meaning that the requested data is unrecoverable from that drive. This is a serious sign of potential media damage or a failing drive, and it often triggers a backup restore or drive replacement, especially in redundant systems where a rebuild might be attempted. It’s specifically about failing to read data, not about writing data, undefined status, or a device being disconnected.