Writeback cache mirroring | Unity 380F

Dear experts,

It appears that described below behaviour leads to slow performance of synchronous writes for our database systems. 

https://www.delltechnologies.com/asset/en-us/products/storage/industry-market/h15162-dell_emc_unity-high_availability.pdf

"Dell Unity uses a mirrored write-back cache. This means for every write, the data is first written to the local SP’s write cache and then it is copied to the peer SP’s write cache over the Common Messaging Interface (CMI) bus. After the data has been mirrored, the acknowledgement is then sent to the host. Since the data written to write cache is fully mirrored between SPs, it is always protected."

If for some reason one of the SPs dies and no mirroring occurs, we see a significant boost in average wait time for sync writes.
Is there any way to change the above behaviour and send acknowledgement before cached data is mirrored?
We should be still fine as cache is protected by BBU, correct?