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One feature of a hyper-converged platform is the use of a scale-out, building block architecture. Leading hyper-converged startups offer these hardware building blocks with their own badge on the server box, but most organizations deploying hyper-converged infrastructure have an existing estate of hardware. Some of this hardware may not be old enough to retire, so can it be integrated with new hyper-converged platforms? Most vendors -- Nutanix, SimpliVity, and partners of VMware EVO:RAIL or Atlantis -- ship hardware, and their software runs exclusively on that hardware. The two optional integration points for all vendors will be:
- Making hyper-converged storage available to existing servers.
- Having existing storage available to hyper-converged servers.
For vendors such as Maxta and Springpath that offer their hyper-converged infrastructure as software-only, it is natural to bring your own hardware. But you still need to access existing hardware for migration.
All hyper-converged platform vendors make their hyper-converged storage available using IP over Ethernet. They also provide some way for other servers, running the same hypervisor, to access this storage. The main differentiator is whether this is intended for long-term use. VMware's EVO:RAIL uses VSAN for storage. VSAN provides storage to every ESXi server in the VSAN cluster, whether it contributes storage or not. Similarly, SimpliVity allows existing ESXi servers to access its hyper-converged storage as compute nodes. Adding compute nodes allows the very efficient storage to be accessed by more compute capacity. Both VSAN and SimpliVity allow non-hyper-converged nodes for long-term access as a central part of the product. SimpliVity and VSAN customers can scale compute capacity without scaling storage.
Other vendors view this type of access as being for migration only. For example, Nutanix allows external server access to its data stores, but it doesn't encourage long-term use. The firm's objective is to simplify the process of getting VMs off your old storage and onto Nutanix badged hardware. External server access with Nutanix is not as tolerant of faults as some other vendors.
External storage with a hyper-converged platform
Integrating existing storage into a hyper-converged platform is desirable for migration. But using external storage with your hyper-converged infrastructure for the long term can be a management challenge.
One objective of hyper-convergence is to remove the storage silo. Accessing existing storage from the hyper-converged infrastructure doesn't remove the silo, and vendors may not support external storage for long-term operation. For example, Fibre Channel SANs are not a feature of hyper-converged storage, so hyper-converged infrastructure vendors do not include FC adapters in servers. In addition, many hyper-converged servers have no capacity to add FC adapters, and those that do may not have support from the hyper-converged vendor.
This is where software-only options will be more accommodating, since their business model does not require users to buy their hardware. If your existing storage is IP based, iSCSI or NAS, access will be easier. Just configure the hyper-converged servers for access to the IP storage the same as you would any other hypervisor. The storage management integration included in your hyper-converged infrastructure will not be available for storage that is not provided by the hyper-converged platform. This means integrated backup and replication provided by the hyper-converged infrastructure will not work with external storage.
If your hyper-converged platform will reuse your existing servers or storage, you need to evaluate this ahead of time. Ensure the platform supports external access and that you don't sacrifice its features to use existing hardware. If you decided on hyper-convergence to simplify operations, using existing hardware may dilute this benefit. If you need to reuse existing assets look at a software-only hyper-converged product. Otherwise, external compute servers may be the only good way to reuse your existing investment.
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