CEPH is a popular open source storage software. However its write latencies are high. VirtuCache caches CEPH volumes to in-host SSDs and by doing so reduces VM level latencies considerably.
D&B uses VirtuCache to Improve the Performance of Equallogic Appliances for VMware VMs and Bare-Metal Linux Servers
By deploying VirtuCache in Dun & Bradstreet's VMware environment, we demonstrated sub 10ms VM latencies for high, write-intensive, random storage IO, which in turn facilitated the P2V of their database servers.