Depending on the selected RAID level and sparing requirements, six types of arrays are  possible, as shown in Figure 4-3. Tip:  Remember that larger drives have a longer rebuild time. Only RAID 6 can recover  from a second error during a rebuild due to the extra parity. RAID 6 is the best choice for  systems that require high availability, and is therefore the default.  After the arrays are created, the next task is to define a  rank . A rank is a logical  representation of the physical array formatted for use as FB or CKD storage types. In the  DS8880, ranks are defined in a one-to-one relationship to arrays. Before you define any  ranks, you must decide whether you will encrypt the data. All drives that are offered in the DS8880 are Full Disk Encryption (FDE)-capable to secure  critical data. In the DS8880, the Encryption Authorization license is included in the Base  Function license group. If you plan to use encryption, you must define an  encryption group  before any ranks are  created .  The DS8880 supports only one encryption group. All ranks must be in this encryption  group. The encryption group is an attribute of a rank. Therefore, your choice is to encrypt  everything or nothing. If you want to enable encryption later (create an encryption group), all  ranks must be deleted and re-created, which means that your data is also deleted. For more information, see the latest version of  IBM DS8880 Data-at-rest Encryption ,  REDP-4500.  Chapter 4. Virtualization concepts  109 Encryption group 4.3.3 Ranks Figure 4-3 RAID array types GLYPH<g2>GLYPH<g18>GLYPH<g18>GLYPH<g14>GLYPH<g22>GLYPH<g1>GLYPH<g19>GLYPH<g16>GLYPH<g20>GLYPH<g15>GLYPH<g1> GLYPH<g2>GLYPH<g18>GLYPH<g18>GLYPH<g14>GLYPH<g22>GLYPH<g1> GLYPH<g10>GLYPH<g1> GLYPH<g10>GLYPH<g1> GLYPH<g12>GLYPH<g2>GLYPH<g9>GLYPH<g5>GLYPH<g1>GLYPH<g31>GLYPH<g1> GLYPH<g32>GLYPH<g1>GLYPH<g34>GLYPH<g1>GLYPH<g10>GLYPH<g1>GLYPH<g23>GLYPH<g8>GLYPH<g10>GLYPH<g7>GLYPH<g6>GLYPH<g24>GLYPH<g1> GLYPH<g33>GLYPH<g1>GLYPH<g34>GLYPH<g1>GLYPH<g10>GLYPH<g1> GLYPH<g10>GLYPH<g1> GLYPH<g11>GLYPH<g1> GLYPH<g13>GLYPH<g1> GLYPH<g10>GLYPH<g1> GLYPH<g11>GLYPH<g1> GLYPH<g12>GLYPH<g2>GLYPH<g9>GLYPH<g5>GLYPH<g1>GLYPH<g32>GLYPH<g1> GLYPH<g31>GLYPH<g1>GLYPH<g34>GLYPH<g1>GLYPH<g10>GLYPH<g1>GLYPH<g34>GLYPH<g1>GLYPH<g11>GLYPH<g1>GLYPH<g34>GLYPH<g1>GLYPH<g13>GLYPH<g1> GLYPH<g32>GLYPH<g1>GLYPH<g34>GLYPH<g1>GLYPH<g10>GLYPH<g1>GLYPH<g34>GLYPH<g1>GLYPH<g11>GLYPH<g1> GLYPH<g2>GLYPH<g1> GLYPH<g3>GLYPH<g1> GLYPH<g4>GLYPH<g1> GLYPH<g13>GLYPH<g1> GLYPH<g2> ’ GLYPH<g1> GLYPH<g3> ’ GLYPH<g1> GLYPH<g4> ’ GLYPH<g1> GLYPH<g13>GLYPH<g1> GLYPH<g2>GLYPH<g1> GLYPH<g3>GLYPH<g1> GLYPH<g4>GLYPH<g1> GLYPH<g5>GLYPH<g1> GLYPH<g2> ’ GLYPH<g1> GLYPH<g3> ’ GLYPH<g1> GLYPH<g4> ’ GLYPH<g1> GLYPH<g5> ’ GLYPH<g1> GLYPH<g12>GLYPH<g2>GLYPH<g9>GLYPH<g5>GLYPH<g1>GLYPH<g27>GLYPH<g26>GLYPH<g1> GLYPH<g29>GLYPH<g21>GLYPH<g28>GLYPH<g1>GLYPH<g34>GLYPH<g1>GLYPH<g28>GLYPH<g13>GLYPH<g1> GLYPH<g30>GLYPH<g21>GLYPH<g28>GLYPH<g1> GLYPH<g17>GLYPH<g18>GLYPH<g1> GLYPH<g17>GLYPH<g18>GLYPH<g1> GLYPH<g17>GLYPH<g18>GLYPH<g1> GLYPH<g10>GLYPH<g1> GLYPH<g13>GLYPH<g1> GLYPH<g32>GLYPH<g1>GLYPH<g34>GLYPH<g1>GLYPH<g10>GLYPH<g1>GLYPH<g34>GLYPH<g1>GLYPH<g13>GLYPH<g1> GLYPH<g17>GLYPH<g18>GLYPH<g1> (not recommended)