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fixed typo thanks to Giovanni Di Santi

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Remzi Arpaci-Dusseau 2020-09-06 09:27:07 -05:00
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file-raid/README.md
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@ -152,16 +152,17 @@ LOGICAL READ from addr:9 size:4096
read [disk 2, offset 4]
```
You might notice a few things about this example. First, the mirrored RAID-1
assumes a striped layout (which some might call RAID-01), where logical block
0 is mapped to the 0th block of disks 0 and 1, logical block 1 is mapped to
the 0th blocks of disks 2 and 3, and so forth (in this four-disk example).
Second, when reading a single block from a mirrored RAID system, the RAID has
a choice of which of two blocks to read. In this simulator, we use a
relatively silly way: for even-numbered logical blocks, the RAID chooses the
even-numbered disk in the pair; the odd disk is used for odd-numbered logical
blocks. This is done to make the results of each run easy to guess for you
(instead of, for example, a random choice).
You might notice a few things about this example. First, the mirrored
RAID-1 assumes a striped layout (which some might call RAID-10, or
stripe of mirrors), where logical block 0 is mapped to the 0th block
of disks 0 and 1, logical block 1 is mapped to the 0th blocks of disks
2 and 3, and so forth (in this four-disk example). Second, when
reading a single block from a mirrored RAID system, the RAID has a
choice of which of two blocks to read. In this simulator, we use a
relatively silly way: for even-numbered logical blocks, the RAID
chooses the even-numbered disk in the pair; the odd disk is used for
odd-numbered logical blocks. This is done to make the results of each
run easy to guess for you (instead of, for example, a random choice).
We can also explore how writes behave (instead of just reads) with the -w
flag, which specifies the "write fraction" of a workload, i.e., the fraction