I want to briefly discuss layouts. This is a topic will delve into more thoroughly later when we talk about plex creation, but because the "VERITAS Getting Started Guide" talks about them, I'll give you the highlights. This stuff may seem pretty basic now, but the more you work will VERITAS the more you will come to appreciate layouts.
Layout can be thought of as the defining difference between the different types of RAID. Simple RAID's don't really have a layout, you simple write linearly starting at the beginning of the first disk until you hit the end, at this point you start writing the second disk, and so on. Striped RAID's have special type of layout, however. Layouts use the following terms:
stripe width (stwidth): The Amount of data to write to a disk before moving to the next. (Generally 32k by default)
columns (ncolumn): A subdisk.
In the case of a Striped RAID, each subdisk would have a column number. A RAID0 with 4 disks, would have 4 columns. The first disk would be column 0 (remember: everything starts with 0), the second would be column 1, the third would be column 2, and the fourth disk would be column 3. Now, when we build a striped RAID we specify both stripe width (which VERITAS calls "stwidth"), and the number of columns (which VERITAS calls "ncolumns") which is the number of subdisks that are going to have data on them. So, as mentioned earlier, we've got 4 disks, and we know the column numbers for each subdisk. If we assigned a stripe width of 32k, and we wrote some data to the volume, we'd write the data 32k at a time, writing each new 32k chunk to the next column, and wrapping around from the 4th column (column 3) to the 1st column (column 0), untill all the data is written. Refer to the "RAID Theory" course for more on this. If you've got this down, but feel foggy, just roll with it, it'll click later as we build plexes.
Now, RAID5 is very similar because it's striped, it's just a different type of stripe. RAID5 uses a layout called "Left Symmetric Layout", or more commonly as simply "RAID5 layout". It would take me too much time to explain this, so check the book. Read through the "RAID Theory" course if you need help, and then go back to the book. You may have to look twice, but you'll get it.