Dell Storage with Microsoft Storage Spaces Best Practices Guide

Configuring write-back cache (WBC) allows 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 immediately respond back to the host with write completion status. Without write-back cache, the physical disks operate in write-through mode where incoming ‘write’ requests hit slower, traditional hard drives 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 you to 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, then WBC is enabled for the VD.