Answers to Test Your Knowledge

     

A1:	False. RAID 0, i.e., striping, offers potential performance improvements but on its own leaves the underlying RAID 0 volume open to the possibility of data loss should one of the disks in the stripe set fail.
A2:	True. A three-disk RAID 5 stripe set offers 2/3 (66 percent) storage capacity, while a four-disk RAID 5 stripe set offers 3/4 (75 percent) storage capacity. You will never achieve 100 percent storage capacity, as at least one disk's worth of storage will be required for parity data.
A3:	True! This is a tricky question, but here is the thinking behind my answer. You have two RAID arrays that support RAID 0, 1, 0/1, and/or 5. This is your hardware solution to RAID. You are concerned that should you lose an entire enclosure you are now vulnerable to losing all your data. The RAID arrays have no built-in mechanism to duplicate data to another array. You decide to utilize a software mechanism, e.g., software mirroring to duplicate write to your second RAID array. This is your software solution to RAID, i.e., RAID 1. In this way, you are protecting against the failure of an entire RAID array.
A4:	False. A single disk drive on its own is a Single Point of Failure. Utilizing parity data whether it is on one disk or spread across all disks in a RAID 5 group avoids a single disk being a Single Point of Failure. Should you experience two disk failures in any parity-enabled RAID, the solution will render the entire RAID volume unusable. A common solution to this is to implement a "hot-standby disk" which will takeover in the event of a failure, reproducing real/parity data from the remaining disk in the RAID volume.