Determine if you want Ring-level protection based on the following:
- HSL failures are rare compared with other disk-related hardware failures.
- If an HSL fails, disk I/O operations might continue, but other hardware is lost (such as work stations, printers and communication lines) making the system unusable.
To achieve ring-level protection, all disk units that are present in the expansion unit in the first HSL must also have a mirrored units present in another expansion unit in the second HSL. The figure shows the elements of ring-level protection: two HSL rings, connected to two expansion units that each contain two buses that are attached to separate IOPs, IOAs, and disk units, respectively.