Applications are unresponsive (SAP/SQL/..) ME4 in HA cluster

Hi everione. I have problem where my applications are slow. Especialy application what have something to do with databases like SAP B1 based on SQL server. Other ... aplication also comunicating with Firebird database are showing in top of window next to application name  "Name of application .... - Application is not responding" message for few seconds, than they run ..but they do not responding straight forward.

We have strange setup of cluster and I think also pools ine ME4 storage are not set correctly .

ME4 storage has 8SSD disk in first 8 slots and rest is HDD storages. Pool A has 2 disk groups G1 0.0-7 RAID5 and G2 0.8-13 RAID5 and Pool B has another group G3 0.14-...to rest also as RAID5.

Over this Pool is setup tiering. If I understand this well than this mean performance is not using SSD speed but HDD speed. as tiering using HDD in first place. Is that my problem or problem can be in network setup? According to recomendations I suppouse not to use spanning tree protocol to not have big latency. Is that correct. do i supouse to remove VLTI connection between core switches and change them to stack and client infrastructure put outside of this core swithes? They are used as connection between buidings where client connection is going throw separate VLAN. 

Please help me resolve why I had problem to run application smothly. In case you need more info let me know.

thx

Below is how our network connection looks like: