StarWind Virtual SAN supports a single Flash (L2 Cache) Policy:
1. Write-Through, caches writes in both Flash (SSD/NVMe) and the underlying storage, and acknowledges back to the originator when complete in the underlying storage.
With the write-through policy, new blocks are written both to cache layer and the underlying storage synchronously. However, in this mode, only the blocks that are read most frequently are kept in the cache layer, accelerating read operations. This is the only mode available for StarWind L2 cache.
In the case of Write-Through cached data does not need to be offloaded to the backing store when a device is removed or the service is stopped.
In the majority of use cases, if L1 cache is already assigned, there is no need to configure L2 cache.
A StarWind Virtual SAN solution with L2 cache configured should have more RAM available, since L2 cache needs 6.5 GB of RAM per 1 TB of L2 cache to store metadata.