Today the peace in storageland has been disturbed by a post of Storage Swiss, The Problems With Server-Side Storage, Like VSAN. In this post they highlight the problems with VSAN. At the same time Coho Data, developer of flash-tuned scale-out storage appliances, released a post about why converged storage, such as VSAN, only seems to be usefull in a niche area. You can read the full post here. VMware had to respond these “attacks” and released a post countering the problems raised by Storage Swiss. As with every black-and-white story both sides have valid points, so we took the liberty to summarize these valid points. On top, we believe both sides can play a role in your storage need and that is why we believe Open vStorage, as only solution in storage land, is the solution by allowing to mix and match converged storage and external storage.
Valid points for the converged stack:
- VSAN and other converged software stacks typically can run on almost any hardware as they are software based.
- Pricing for a software based solution to give the same reliability as a hardware based solution can be a fraction of the cost and will become commodity over time. Take as example traditional storage redundancy and fault tolerance which is typically implemented via dual controller hardware systems. Software based techniques provide the same level of reliability at much lower costs and much better scaling.
- Converged stacks are VM-centric, treating a single volume as a LUN. This allows for flexibility and cost reduction. Test tiers can only have a limited or no protection and important volumes might be replicated multiple times across the storage pool and run with best performance.
- The network in a converged stack is also less complex as only the hosts need to be connected. With external storage appliances you also need to take the dedicated storage network into account.
- Easy to setup and manage, even for less experienced IT support. This can well be the case in a branch office.
- Running storage as close as possible to the compute power makes sense. If not, we all would be using Amazon S3 to power our VM storage needs.
Valid points for the external storage stack:
- External storage arrays take resource intensive tasks upon themself. It allows for example processor and network resources to manage replication and recovery.
- External storage arrays allow to be linked to different hypervisors while converged infrastructure solutions are tightly linked to the hypervisor. For example VSAN can only be used with the VMware ESXi hypervisor.
- The storage network can be completely separated from the computer and outbound traffic.
- Better usage of flash drives as they are shared between multiple hypervisors and writes don’t have to be mirrored to a second appliance.
The Open vStorage view:
Open vStorage believes there isn’t a ‘One Size Fits All’ solution to storage demands. Today, specific applications and functionalities demand specific storage. That is why Open vStorage is configured to work as a truly open solution and works with any storage backend. Open vStorage provides the flexibility of using an existing distributed file system, external storage appliances and even object stores. This allows for more flexibility but at the same time keeps the ability to protect existing investments.
We are firm believers in the approach taken by VMware vSAN where software running on a cluster of machines provides you a reliable storage pool and where the storage intelligence is moved closer to the compute layer. However, we believe this is too important a piece of the virtualization stack for a proprietary solution that is either hypervisor specific, hardware specific, management stack specific and storage back-end specific. Our goal behind Open vStorage is not only build something open and non-proprietary but something modular enough which allows developers and hardware manufacturers to innovate on top of Open vStorage. We believe with contributors from the open source community Open vStorage can become a far superior compared to proprietary offerings whether these be hardware or software based.
To conclude Open vStorage:
- Leverages server based flash and storage back-ends to create shared virtual machine storage
- Redundant, shared storage without the costs and scaling problems of dual controller systems
- Works with any storage back-end, including filesystems, NAS, S3 compatible object storage, …
- Works with KVM and VMware
- Delivered under the Apache License, Version 2.0