VMware Virtual SAN is a brand new software defined storage system. Through extending the vSphere virtual management program, computing resources and directly attached storage are fused together. By clustering servers with directly attached HDDs and SSDs, Virtual SAN can create distributed and shared storage specifically designed and optimized for virtual machines. Virtual SAN, which is built-in within the vSphere core, adopts a distributed architecture; and can utilize PCIe Flash to provide high performance read/write cache function. In hybrid-mode VSAN environment, PCIe Flash works as Tier-1 R/W cache, while HDD as Tier-2 storage; in all flash mode, PCIe Flash serves as Tier-1 storage and is reserved for write only; and at Tier-2 storage, another PCIe Flash persists data store and provides read access only, thus achieving read/write separation.
In hybrid VSAN, Shannon Direct-IO™ PCIe Flash functions as:
1.Read cache: stores Tier 1 hot data, and reduces I/O latency as cache read hits.
2.Write cache: function as non-volatile write cache. Write commands are issued to PCIe Flash; to reduce write latency, then data will be transferred to Tier2 HDD at an appropriate time.
Shannon Direct-IO™ PCIe Flash combined with VSAN can significantly improve the performance of virtual machines. VSAN elevates the I/O performance by exploiting the performance characteristic of SSD, while retaining capacity scale-out characteristics of HDD.
Features of Shannon Direct-IO™ PCIe Flash in all flash VSAN:
1.Low latency non-volatile Tier 1 write cache.
2.High capacity and high performance Tier 2 persistent data store.