Acer Altos R920 Series - Manual (Page 199)

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Initializing the RAID volume
You can skip this procedure if you selected to create a new IM array
(or pressed D) while performing the creating a RAID 1 volume with
a hot spare disk section. After you create a new IM array, no
synchronization will be performed. You can exit the SAS configuration
utility and proceed to install the OS.
Exiting the SAS configuration utility
In the SAS configuration utility, press Esc twice and select Exit the
Configuration Utility.