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Hardware Redundancy Transcription

Welcome to our system resilience and fault tolerance module. In this module, we will discuss hardware redundancy. It is important to make sure that we minimize our down time, especially with our critical systems. We can use hot spares to make sure that failed components are automatically replaced without taking the system down.

The mean time between failure or MTBF is a way for us to calculate the expected lifetime of one of our components such as a hard drive or power supply. Here, we can calculate the risk of failure and use this to compare devices. For am mission critical system, we would want to purchase a device with a high mean time between failure so that it will last longer.

Mean time to repair or MTTR is the amount of time it will take for us to get the device back into production if it fails while it is operating. Mean is another way of saying average. You should be familiar with the MTBF and the MTTR for the CISSP exam, and be aware of what the difference is between these two terms.

With RAID technology, we can use several disk and make them appear as one disk in order to increase performance or fault tolerance. RAID stands for redundant array of inexpensive disks, or redundant array of independent disks. It allows you to create fault tolerance against a single disk failure. Meaning that if one disk fails, the rest of the disks will work to make sure that no data is lost, and that the system continues to function until you can replace that disk.

In order to do this, it separates the data into multiple units on multiple disks. And this process is called striping. We usually use this with servers to reduce downtime. And we can use parody data in order to rebuild a lost disk. So if a disk fails, we can simply install a new disk and then use parody data to rebuild the data that was lost on that bad drive.

There are several common RAID levels. RAID Level 0 stripes the data across multiple disks, but provides no fault tolerance. This is only for high performance. If one of the drives in the array goes bad you will lose data. With level 1 you have mirroring where there is an exact copy of your data on two hard drives.

With RAID Level 5, we have striping with parity. We interleave parity across three or more disks. With Raid Level 5, we can lose one disk and not lose any data. With Raid Level 6, we have double parity. And in this system, two of the drives can fail. When we combine RAID Level 0 and 1, we call this RAID 10.

And this is commonly used in servers and data centers. Here we're combining striping and mirroring. The striping is for performance and the mirroring is for redundancy. And we can survive the failure of two disks without losing any data. For the CISSP exam, you want to remember that RAID 6 and RAID 10 are able to lose two disks without losing any data. RAID one and RAID five you can only lose one drive. And with RAID 0 you cannot lose any drives. RAID zero is not designed for fault tolerance. This concludes our system resilience and fault tolerance module. Thank you for watching.

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