8456ch_Virtualization_Concepts.fm Draft Document for Review December 5, 2019 4:33 pm Rotate volumes allocation method 114  IBM DS8900F Architecture and Implementation Figure 4-9 Rotate volumes Extents can be allocated sequentially. In this case, all extents are taken from the same rank  until enough extents are available for the requested volume size or the rank is full. In this  case, the allocation continues with the next rank in the extent pool.  If more than one volume is created in one operation, the allocation for each volume starts in  another rank. When several volumes are provisioned (allocated), rotate through the ranks, as  shown in Figure 4-9. You might want to consider this allocation method when you prefer to manage performance  manually. The workload of one volume is going to one rank. This configuration makes the  identification of performance bottlenecks easier. However, by putting all the volumes’ data  onto one rank, you might introduce a bottleneck, depending on your actual workload. Important:  Rotate extents and rotate volume EAMs provide distribution of volumes over  ranks. Rotate extents run this distribution at a granular (1 GiB or 16 MiB extent) level, and  is a better method to minimize hot spots and improve overall performance. However, as previously stated, Easy Tier is really the preferred choice for managing the  storage pool extents. In a mixed-tier characteristic extent pool that contains different  tiers  of ranks, the storage pool  striping EAM is used independently of the requested EAM, and EAM is set to  managed . Easy Tier  default allocation order is  High Performance . With the  High Performance  setting,  the system will populate drive classes in this order: Flash Tier 0, Flash Tier 1, Flash Tier 2. There is a GUI and a CLI option for the whole Storage Facility to change the allocation  preference. The two options are  High Performance  and  High Utilization . With the  High  Utilization  setting, the machine will populate drive classes in this order: Flash Tier 1, Flash  Tier 2, Flash Tier 0. The CLI  chsi  command can be used to switch the  ETTierOrder parameter between  High Performance  and  High Utilization . When you create striped volumes and non-striped volumes in an extent pool, a rank might be  filled before the others. A full rank is skipped when you create new striped volumes. GLYPH<g2>GLYPH<g3>GLYPH<g4>GLYPH<g5>GLYPH<g1>GLYPH<g6> GLYPH<g7>GLYPH<g6>GLYPH<g8>GLYPH<g9>GLYPH<g10>GLYPH<g11> GLYPH<g2>GLYPH<g3>GLYPH<g4>GLYPH<g5>GLYPH<g1>GLYPH<g12> GLYPH<g7>GLYPH<g6>GLYPH<g8>GLYPH<g9>GLYPH<g10>GLYPH<g11> GLYPH<g2>GLYPH<g3>GLYPH<g4>GLYPH<g5>GLYPH<g1>GLYPH<g13> GLYPH<g7>GLYPH<g6>GLYPH<g8>GLYPH<g9>GLYPH<g10>GLYPH<g11> GLYPH<g2>GLYPH<g3>GLYPH<g4>GLYPH<g5>GLYPH<g1>GLYPH<g14> GLYPH<g7>GLYPH<g6>GLYPH<g8>GLYPH<g9>GLYPH<g10>GLYPH<g11> GLYPH<g1>GLYPH<g2>GLYPH<g3>GLYPH<g4>GLYPH<g3>GLYPH<g5>GLYPH<g6>GLYPH<g11> GLYPH<g2>GLYPH<g12>GLYPH<g13>GLYPH<g14>GLYPH<g5>GLYPH<g10> GLYPH<g15> GLYPH<g16>GLYPH<g17>GLYPH<g18>GLYPH<g19>GLYPH<g20>GLYPH<g1>GLYPH<g6>GLYPH<g1>GLYPH<g21>GLYPH<g1>GLYPH<g6>GLYPH<g22>GLYPH<g9>GLYPH<g10> GLYPH<g15> GLYPH<g16>GLYPH<g17>GLYPH<g18>GLYPH<g19>GLYPH<g20>GLYPH<g1>GLYPH<g12>GLYPH<g1>GLYPH<g21>GLYPH<g1>GLYPH<g12>GLYPH<g12>GLYPH<g9>GLYPH<g10> GLYPH<g15>GLYPH<g16>GLYPH<g17>GLYPH<g18>GLYPH<g19>GLYPH<g20>GLYPH<g1>GLYPH<g12>GLYPH<g1>GLYPH<g21>GLYPH<g1>GLYPH<g23>GLYPH<g9>GLYPH<g10> GLYPH<g15> GLYPH<g16>GLYPH<g17>GLYPH<g18>GLYPH<g19>GLYPH<g20>GLYPH<g1>GLYPH<g14>GLYPH<g1>GLYPH<g21>GLYPH<g1>GLYPH<g6>GLYPH<g13>GLYPH<g9>GLYPH<g10> GLYPH<g15> GLYPH<g16>GLYPH<g17>GLYPH<g18>GLYPH<g19>GLYPH<g20>GLYPH<g1>GLYPH<g24>GLYPH<g1>GLYPH<g21>GLYPH<g1>GLYPH<g6>GLYPH<g12>GLYPH<g9>GLYPH<g10>