A systems administrator is investigating a report of extremely slow write performance on a file server's primary storage array. The server uses a hardware RAID 10 configuration with a dedicated controller. The administrator checks the RAID management utility and observes the following:
All physical disks in the array are reported as "Online" and "Healthy".
A persistent alert states: "Write-back cache is temporarily disabled."
I/O statistics show abnormally high write latency.
What is the MOST likely cause of this issue?
A single drive in the RAID array has developed bad sectors.
The storage array is undergoing a rebuild process.
The server's network interface card (NIC) is misconfigured.
The correct answer is that the RAID controller's cache battery has failed. RAID controllers use a battery backup unit (BBU) to protect data stored in the volatile write-back cache in the event of a power failure. If the controller detects that the battery has failed or can no longer hold an adequate charge, it will disable the write-back cache as a safety measure to prevent data loss. The controller then switches to write-through mode, where data is written directly to the disks, which is significantly slower and results in the high write latency reported. The other options are incorrect because the array is not rebuilding, a NIC issue would not cause this specific alert or I/O pattern, and the drives are reported as healthy.
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What is RAID write-back cache and write-through mode?
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