Home > Storage > PowerMax and VMAX > Storage Admin > Dell PowerMax: Data Reduction > Data Reduction I/O flow
All I/O is passed through cache and then processed by the system. This means data reduction actions are performed after the data is received by the system, but before it is placed on disk. Using an inline process requires additional checks within the I/O flow where data reduction applies. The system uses these checks to determine whether incoming data needs to pass through the data reduction hardware or not. Incoming data for a storage group with data reduction enabled will follow the data reduction flow. However due to the activity-based compression (ABC) function, active data for a storage group with data reduction enabled will skip the data reduction flow for performance optimization. Data not compressed due to ABC may be compressed later and moved to a compression pool. Data for a storage group with data reduction disabled will ignore the data reduction flow and will be written to the system unreduced.
There are a few different I/O types to consider, Read, Write, Write-update.
The following figure describes the path the I/O will follow which is determined by characteristics of the dataset or the related storage group.