A systems administrator is investigating performance issues on a Linux file server that uses a RAID 5 array. Users report that accessing certain large files is extremely slow or results in errors. The administrator inspects the kernel message buffer with the dmesg command and finds numerous "I/O error" messages that reference a single drive in the array, /dev/sdc. A subsequent check of this drive's SMART status reveals a high and increasing "Reallocated_Sector_Ct". The other drives in the array show no errors.
Based on this information, what is the MOST likely cause of the problem?
The correct answer is Media failure. The combination of I/O errors logged against a specific drive and an increasing count of reallocated sectors in the drive's SMART data are classic indicators of a physical media failure. This means the surface of the disk platter is degrading, and the drive is moving data from these failing sectors to spare sectors. This process leads to significant performance degradation and is a strong predictor of imminent total drive failure.
Controller failure is less likely because the errors are isolated to a single drive. A failing RAID controller would typically cause issues across all drives in the array.
Misconfigured RAID is a logical issue related to the array's setup, which would not generate physical I/O errors or cause SMART attributes related to bad sectors to change on an individual drive.
Loose connectors could cause I/O errors, but they would not account for the SMART data showing a persistent and increasing number of reallocated sectors, which indicates permanent physical damage to the drive's media.