Dell Storage with Microsoft Storage Spaces Best Practices Guide

Configuring write-back cache (WBC) allows Microsoft Storage Spaces to use a portion of available disk space of the SSDs to provide low latency cache for incoming write commands. All incoming write requests are cached on SSDs and host immediately receives a write completion status. Without write- back cache, the physical disks operate in write-through mode where incoming write requests hit slower, traditional HDDs before responding with completion. Using WBC can make a significant performance improvement to almost all workloads.

To use WBC, you must have SSDs in a storage pool. The default disk space of WBC is 1 GB and can be changed when creating a VD. Dell recommends that you use the default WBC disk space.

Whenever you create a VD, as long as the SSD tier disk space is greater than either the default or specified WBC disk space and you have the minimum number of SSDs in the storage pool to enable WBC for the resiliency setting and WBC is automatically enabled for the VD.