Is PrimoCache compatible with DirectStorage?

Yes, PrimoCache is compatible with BypassIO and DirectStorage starting from version 4.3.0. You can run the following command from a command prompt running as administrator to find out whether you get BypassIO support and why there may be an incompatibility.
    fsutil bypassio state /v <path>
Where <path> can be a volume, a directory, or a specific filename.

It is important to note that if a logical volume is cached with Defer-Write enabled, BypassIO requests to this volume will be automatically blocked by PrimoCache. This is to prevent possible data inconsistency issues. DirectStorage bypasses all intermediate drivers such as PrimoCache and reads data directly from the disk. The deferred write-data may still be in the cache and has not yet been written to the disk. Therefore, the data read by DirectStorage may not be the latest, leading to data inconsistency. At this time, if you run the above command, PrimoCache will report "Volume with write-back caching is not supported". If you want to make this volume compatible with DirectStorage, you need to turn off Defer-Write.