A company has two PowerMax arrays located 100 km apart.

Fast Write is a Dell EMC technology that improves Fibre Channel (FC) replication between sites in a SRDF/S configuration. When a write I/O is issued by the host to the R1 device, SRDF with Fast Write acknowledges the write to the host as soon as the data is stored in the R1’s cache and transmitted to the R2’s cache. This results in reduced latency and improved performance for FC replication between sites.

https://www.delltechnologies.com/asset/en-us/products/storage/industry-market/h17118_dell_emc_powermax_family_overview.pdf

https://infohub.delltechnologies.com/l/dell-emc-powermax-and-vmax-all-flash-srdf-metro-overview-and-best-practices-1/srdf-metro-overview/