RAID level 1 refers to disk mirroring with block striping. Figure 10.3b shows
a mirrored organization that holds four disks’ worth of data.
Note that some vendors use the term RAID level 1+0 or RAID level 10 to refer
to mirroring with striping, and use the term RAID level 1 to refer to mirroring
without striping. Mirroring without striping can also be used with arrays of
disks, to give the appearance of a single large, reliable disk: if each disk has
Mblocks, logical blocks 0 to M− 1 are stored on disk 0, Mto 2M− 1 on disk
1(the second disk), and so on, and each disk is mirrored.2