Server 2012 R2 Disk Troubleshoot

My Windows Server 2012 R2 box has begun throwing disk-related error messages and overall performance has slowed to a crawl. I am not sure whether the root cause is hardware (drive, RAID controller, cabling) or software (file-system corruption, drivers, services), and I need a seasoned Windows server engineer to zero in on the problem and fix it.

What I am seeing
• System logs routinely flag disk errors and the server hesitates during read/write operations.
• General responsiveness is sluggish even under light load.

Your task
1. Connect remotely, collect diagnostics with the tools you trust—Event Viewer, CHKDSK, S.M.A.R.T. data, PowerShell, PerfMon, vendor utilities, etc.—and identify the precise failure point.
2. Recommend and carry out the corrective action: firmware update, bad-sector repair, driver roll-back, controller rebuild, or full hardware replacement if needed in our office visiting.
3. If required to replace any hardware, we will arrange the same and you need to visit in our office and replace the hardware and configure the server if required any changes.
4. Verify that the error messages no longer appear and that performance is back to normal, documenting the steps taken so I can reference them later.

Acceptance criteria
• Server boots cleanly with no disk-related warnings or critical events in the log for 24 hours.
• Read/write benchmarks (CrystalDiskMark or similar) match healthy baseline figures.
• A brief report summarizing findings and fixes is delivered.