Here is a S2300 storage, and its power of B controller is off. We find that host IO capability decline seriously.
Turn on the power, and cache writing strategy changes to write back automatically. Storage IO capability get right.
1. From log of storage, a log come out as follow after power of B controller is off:
Apr 17 00:29:06 OceanStor kernel: Remote set write through complete in poweron when fault.
2. This log indicate that cache writing strategy of B controller has changed from write back to write through. So when you access lun, IO capability declines.
When a storage works with single power, it is hard to mark sure that cache data of two controller is written to hard disk. So in order to ensure security of data, it will adjust writing strategy automatically.