I do understand RAID 1. You have two drives that are mirrored. So when one drive fails, you have the full set of data on the other drive.
But with RAID 5 you are able to lose a complete drive out of a set of 3 for example. You have full data redundancy without sacrificing half of your capacity. How does this work?
In: 5
RAID 5 is kind of a combination of striping (RAID 0) with what’s called parity.
If you think of the 3 drives as a table with columns and rows, you stripe the data across 2 of the 3 columns in a row, and then calculate the parity in the 3rd column. If you then delete one of the first two cells, you could recalculate it using the parity. It’s not a copy of the data, it’s instructions on how to figure out what data is missing based on another piece of data.
You can actually demonstrate this in Excel. Make 2 columns of random 1s and 0s. In the 3rd column put in the equation “=XOR(A1,B1)” and fill down. In the 4th column do another equation of “=XOR(B1,C1)” and fill down. The data will match the first column. You have 2 pieces of real data and one column that lets you create anything that is missing.
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