Occasionally, a disk may become unavailable or unresponsive to the point where it apparently ‘ejects’ while in use. In the majority of recent cases, this has been due to an ongoing Mac OS hardware bug.
SoftRAID is designed to detect and inform you when any of your disks become unavailable. So, whenever SoftRAID registers that a disk has been ejected—for whatever reason—it will put up a warning automatically.
The workaround for this issue is to open System Preferences, select Energy Saver, and turn off the checkbox settings for “Put hard drives to sleep when possible” (click here for more info).