The Collaborative International Dictionary of English v.0.48:

Rais \Rais\ (r[imac]s), n.
   Same as 2d Reis.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Reis \Reis\ (r[imac]s), n. [Ar. ra["i]s head, chief, prince.]
   A common title in the East for a person in authority,
   especially the captain of a ship. [Written also rais and
   ras.]
   [1913 Webster]

The Free On-line Dictionary of Computing (30 December 2018):

Redundant Array of Inexpensive Servers
RAIS

    (RAIS) The use of multiple servers to provide
   the same service in such a way that service will still be
   available if one or more of the servers fails.  The term may
   or may not imply some kind of load balancing between the
   servers.  See cluster.

   The term "RAIS" follows RAID, which describes schemes for
   resilient disk storage.

   (2007-02-28)