The IBM FlashSystem 9100 system has two different types of enclosures: control enclosures and expansion enclosures. 

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). 

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. 

## 1.1.1 Control 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. 

## 1.1.2 Expansion enclosures 

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: 

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> 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. 

