RAID 5 volumes need fewer disks for data redundancy than mirrors, and therefore can cost less than a RAID 1 (mirror) configuration.
What is the minimum number of slices that a RAID 5 volume must have?
Three (3).
Is there a maximum number of slices a RAID 5 volume can have?
No. The more slices a RAID 5 volume contains, however, the longer read operations take when a slice fails. (By the nature of RAID 5 volumes, write operations are always slower.)
How do I expand a RAID 5 volume?
By concatenating slices to the existing part of a RAID 5 volume.
When I expand a RAID 5 volume, are the new slices included in parity calculations?
Yes.
You cannot use a RAID 5 volume for root (/), /usr, and swap, or existing file systems.
Is there a way to recreate a RAID 5 volume without having to "zero out" the data blocks?
Yes. You can use the metainit(1M) command with the -k option. (There is no equivalent within Enhanced Storage. The -k option recreates the RAID 5 volume without initializing it, and sets the disk blocks to the OK state. If any errors exist on disk blocks within the volume, Enhanced Storage may begin fabricating data. Instead of using this option, you may want to initialize the device and restore data from tape. See the metainit(1M) man page for more information.
Note - When you add a new slice to a RAID 5 volume, Enhanced Storage "zeros" all the blocks in that slice. This ensures that the parity will protect the new data. As data is written to the additional space, Enhanced Storage includes it in the parity calculations.