The issue was related to “max_sectors_kb” value on Linux. I think that EMC should add recommendation value to best practices or connectivity guide for EMC Unity. Also read my blog post about that: I/O Block Size Best Practice on EMC All Flash/Hybrid Flash Array and Linux (Physical And Virtual) - Davoud Teimouri - Virtualization and Data Center
We have an EMC Unity XT 880F for OLTP workload, the storage array is fine even under high usage but there's read cache usage that seems cause of LUN latency. Everything is good on the storage array but overall latency is very high on storage array. Unity XT 880F has more than 700GB SP cache, why latery is high on this All-Flash array?  
EMC Unity: Cache Read Hit - LUN Latency