Hi!
Please check this
KB article.
"The size of L1 cache should be equal to the amount of the average working data set. The total amount of L1 cache assigned influences the time required for system shutdown. Please make sure not to overprovision the L1 cache amount to avoid the service interruption and the loss of cached data.
In case of using L1 cache in write-back mode, UPS units have to be installed to ensure the correct shutdown of StarWind Virtual SAN nodes. If a power outage occurs, this will prevent the loss of cached data. The UPS capacity must cover the time required for flushing the cached data to the underlying storage."