The hardware monitoring software sent a warning alert for a critical file server: the battery on the redundant array of independent disks (RAID) controller had failed. For want of it, the controller had abandoned its write-back cache policy for write-through, and disk write speed fell grievously.

Two duties lay before me: to replace the failed battery, and to restore the write-back cache policy so the server might perform as before.

I scheduled a short maintenance window in the off-peak hours and drew a replacement battery from the hardware inventory. When the window came, I shut the server down safely, removed the power cables, opened the chassis, and sought out the RAID controller. The old battery I disconnected and the new I installed; then I closed the chassis, restored the power cables, and turned on the server.

In the RAID controller management utility during the boot process, I saw the new battery charging correctly, and I returned the cache policy to write-back. The server booted normally. I tested the file transfer speeds; the disk write speed had returned to its normal, high level. I recorded the work in the maintenance log.