The VMware Software-Defined Storage Vision is app-centric and provides policy driven automation. VMware Virtual SAN is a Hyper-converged architecture that can leverage flash, and provides scalability through a distributed architecture. VMware’s product goal was to empower the vCenter administrator to manage there own storage without having deep storage skill sets. It is also important that it works seamlessly with all VMware’s product portfolio and vSphere features.
This vision is reflected in the architecture decisions that were made in developing Virtual SAN. It was decided to use a hyper-converged architecture integrated into the host hypervisor. Because it is a distributed architecture there is no single potential bottle-neck in the framework.
Within Virtual SAN you have the concept of Disk groups. Each host can have up to 5 disk groups per host and up to 40 drives. There are two tiers; a hybrid tier (flash and spinning) and an all flash tier (Note: a different algorithm is used for hybrid and flash tier so you do not want to create a hybrid tier and then manually adjust the disks to flash). In a hybrid tier there is 1 caching device per disk group and 1 – 7 spinning disk (HDD) per disk group. You can let the system autodiscover the drives during the setup or select specific disks.
Virtual SAN uses the flash device for delivering the performance you need. The flash is split between a 70% Reach Cache and a 30% Write-back Buffer. Virtual SAN 6.1 (6.2 is in beta testing) now supports stretched clusters which allows a cluster to span datacenters within a metropolitan network (there is a latency tolerance is this model).
Virtual SAN is tightly integrated into the hypervisor. The storage algorithms are built right into the hypervisor. A demo is displayed showing how vCenter is aware that Virtual SAN data needs to be considered when putting the host in maintenance mode. You have three options: ensure accessibility, full data migration or no data migration. Ensure accessibility is designed for short term maintenance, full data migration for replacing the host.
Virtual SAN is an object-based storage which means it stores a number of objects. Each VM consists of a number of objects which are individually distributed. Virtual SAN is a highly scalable solution. As you increase hybrid disk groups you increase the performance (almost double according to VMware’s internal testing).
VMware is doing allot of work with Tier One Applications like Oracle 11g RAC workloads to measure performance. Results show high performance that is very predictable from a scalability perspective.
Virtual SAN 6.0 also introduced vsanSparse snapshots and clones which allows greater snapshot depth (up to 32 snapshots per object). The important point of vsanSparse is that it has a negligible performance impact. Virtual SAN provides an plugin to provide you all the metrics and measurements within the vSphere Web Client. This allows you to see exactly what is happening in the Virtual SAN cluster performance. This visibility has been extended to vRealize Operations so that you have visibility on multiple Virtual SAN clusters.
From a roadmap perspective deduplication as well as end-to-end protection for data over the network and at rest through software based checksums.