Im using a PERC 3/DC controller to run a RAID 5 array using 4 hard disks. I am hoping to change this to 3 disks in the array and 1 hot spare. Is it possible to remove 1 disk from the array, reconfigure it as a hot spare, then reconfigure the RAID 5 array to use 3 disks WITHOUT loosing any data? I have backups but I would rather just reconfigure it without going through the hassle of restoring data. Thanks!
No, and if you have 4 disks and want two spares you are better off performance wise with a 4 disk RAID 10 instead of a 3 disk RAID 5 + hot spare. Either way your array will have 2 disks worth of usable capacity but the RAID 10 will have better write speeds and takes less time to recover from a failed disk.
Assuming the RAID 5 doesn't contain your boot volume, I'd go ahead and backup the data, reconfigure to a RAID 10, and restore the data.
RAID Level Comparison for arrays up to 8 drives. Features RAID 0 RAID 1 RAID 5 RAID 6 RAID 10 Min Drives 2 2 3 4 4 Data Protection 0 1 1 2 2 (Up to one disk failure in each sub-array) Read Performance High High High High High Write Performance High Medium Low Low Medium Degraded Read Perf N/A Medium Low Low High Degraded Write Perf N/A High Low Low High Capacity Utilization % 100 50 67-87 50-75 50