The IBM FlashSystem 9100 system has two different types of enclosures: control enclosures  and expansion enclosures. Each control enclosure can have multiple attached expansion enclosures, which expands the  available capacity of the whole system. The IBM FlashSystem 9100 system supports up to  four control enclosures and up to two chains of SAS expansion enclosures per control  enclosure. The IBM FlashSystem 9100 control enclosure supports up to 24 NVMe capable flash drives  in a 2U high form factor.  There are two standard models of IBM FlashSystem 9100: 9110-AF7 and 9150-AF8. There are also two utility models of the IBM FlashSystem 9100: the 9110-UF7 and 9150-UF8. Note:  The IBM 9848-UF7 and 9150-UF8 are the IBM FlashSystem 9110 with a three-year  warranty, to be utilized in the Storage Utility Offering space. These models are physically  and functionally identical to the IBM FlashSystem 9848-AF7 and AF8 respectively, with the  exception of target configurations and variable capacity billing.  The variable capacity billing uses IBM Spectrum Control™ Storage Insights to monitor the  system usage, allowing allocated storage usage above a base subscription rate to be billed  per TB, per month. Allocated storage is identified as storage that is allocated to a specific  host (and unusable to other hosts), whether data is written or not. For thin-provisioning, the  data that is actually written is considered used. For thick provisioning, total allocated  volume space is considered used.  New SAS-based small form factor (SFF) and large form factor (LFF) expansion enclosures  support flash-only MDisks in a storage pool, which can be used for IBM Easy Tierfi: Chapter 1. IBM FlashSystem 9100 introduction  3 GLYPH<SM590000> The new IBM FlashSystem 9100 LFF expansion enclosure Model A9F offers new tiering  options with solid-state drive (SSD flash drives). Up to 736 drives of serial-attached SCSI  (SAS) expansions are supported per IBM FlashSystem 9100 control enclosure. The  expansion enclosure is 5U high. GLYPH<SM590000> The new IBM FlashSystem 9100 SFF expansion enclosure Model AAF offers new tiering  options with solid-state drive (SSD flash drives). Up to 480 drives of serial-attached SCSI  (SAS) expansions are supported per IBM FlashSystem 9100 control enclosure. The  expansion enclosure is 2U high. GLYPH<SM590000> An  expansion enclosure  enables you to increase the available capacity of the IBM  FlashSystem 9100 cluster. it communicates with the control enclosure via a dual pair of  12 Gbps SAS connections. These expansion enclosures can house a large number of  flash (SSD) SAS type drives, depending on which model of enclosure is ordered.  GLYPH<SM590000> A  control enclosure  manages your storage systems, communicates with the host, and  manages interfaces. In addition, it can also house up to 24 NVMe capable flash drives.  These drives can be either industry-standard NVMe type or the exclusive IBM NVMe  FlashCore Modules (FCM). 1.1.1 Control enclosures 1.1.2 Expansion enclosures