Drobo Robotics User Manual page 36

Dual disk redundancy is a setting that will protect your stored data
against two simultaneous drive failures. When this additional safeguard
is enabled, the amount of usable space is reduced in order to provide
this protection. To use dual disk protection, you are required to have at
least three hard disks in your DroboPro and sufficient free disk space.
By default, this setting is disabled. To enable it, go to the Advanced
Controls > Tools tab and click the Settings button in the DroboPro
settings section. Dual disk protection can be enabled or disabled at
anytime as long as you meet the minimum requirements mentioned
above.
By default, DroboPro automatically spins down the hard disks after 15
minutes of inactivity. This helps save electricity and can prolong the life
of the drives. The one drawback is that it will take the DroboPro a few
moments to spin the drives back up. If you would like to change this
setting, go to the Advanced Controls > Tools tab and click the Settings
button in the DroboPro settings section.
The iSCSI window allows you to configure your iSCSI connection on your
DroboPro. "Automatically configure" (default) allows Drobo Dashboard
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