High Speed Storage is Back in the VMware Host with Hyper Converged Infrastructure and Host Side Caching, but the similarities end there….
The main advantage that hyper-converged infrastructure(HCI) has over traditional converged infrastructure (separate hardware for compute and storage) is that HCI has put high speed storage back in the compute nodes. This is also true for Host Side Caching software, with the added benefit that host side caching maintains the flexibility that Converged Infrastructure (CI) always had over HCI, that of being able to scale and do maintenance on compute and storage hardware independently of each other.
Other pros of host side caching + converged versus hyper-converged infrastructure are listed below.
Ease of deployment. Hardware refresh not needed. Host side caching is drop-in software for existing converged infrastructure. It can be deployed in minutes and without any maintenance mode/downtime for VMware or storage. Deploying HCI is more complicated and most likely will require new server hardware. Host side caching on the other hand requires only a SSD (or spare RAM) in the ESXi host.
Faster recovery from failure situations. In HCI, because the same motherboard is responsible for storage and compute operations, host failure/maintenance mode results in degraded storage, and vice-versa. For instance, host shutdown takes longer since all the local data needs to be redistributed to other hosts; SSD failure might result in host down. In general, recovery times are longer. On the other hand, in case of host side caching, since in-host cache has transient data only and the backend storage array is still the system of record, recovery times in case of host or SSD failure are only marginally longer. More details on differences in handling of failure situations are at this link, that explains the storage IO path in VirtuCache and VSAN.
Less Vendor Lock-in. Converged infrastructure has always had less vendor lock-in than HCI because compute connects to storage using standardized protocols like iSCSI or FC, as a result a storage array or server vendor can be swapped for another. Installing host side caching doesn’t change this dynamic. Conversely in HCI, vendor specific protocol is used to connect locally attached storage to ESXi, and so you are locked-in to the HCI vendor for both storage and compute.
Host side caching software can use large amounts of RAM. If host RAM is used as cache media, your CI infrastructure will be higher performing than any HCI solution since HCI solutions are not capable of using large amounts of RAM for storage IO acceleration.
VirtuCache is host side caching software from us, that you install in ESXi hosts. It then caches frequently used data from any SAN based storage to in-host SSD or RAM. It’s very easy to install and is entirely non-disruptive to existing VMware + SAN deployments. You can evaluate it by clicking on this ‘Download Trial’ link.