Data placement is performed using a process called compaction. Compaction intuitively places reduced or unreduced data on disk in the best possible location available. The operation of storing data on disk uses write objects. Each object is 6 MB of contiguous back-end data-device capacity across the drives configured in the system. Write objects are aligned on 1 K boundaries and are consumed sequentially in a single use. Write objects are spread across full stripes for all supported RAID types to optimize writes. Each object supports reduced or unreduced data for both fixed-block architecture (FBA) and CKD emulation.
- FBA write object: An unreduced write object consists of 48 FBA tracks. A reduced write object consists of 1,000 reduced tracks. Reduced entries for write objects range from 1 KB to 96 KB.
- CKD write object: An unreduced write object consists of 108 CKD tracks. A reduced write object consists of 1,000 reduced tracks. Reduced entries for write objects range from 1 KB to 52 KB.
