NAS refers to a storage device that is connected directly to your network. Any user or device with access to your network can access the available storage provided by the NAS. NAS storage is easily scalable and can add data redundancy through RAID technology. NAS uses the file storage format.
NAS storage may or may not be the first choice in terms of enterprise storage, but it does have a solid market appeal as an on-premises primary backup storage solution.
A SAN is a dedicated network of pooled storage devices. The dedicated network, separate from the regular network, provides high speed and scalability without concern for the regular network traffic. SANs use block storage format and can be divided into logical units that can be shared between servers or segregated from other servers. SANs can be accessed by multiple servers and systems at the same time. SANs are scalable and offer high availability and redundancy through RAID technology.
SANs can use a variety of disk types and sizes and are quite common among on-premises storage solutions.
“Software-defined storage (SDS) is a storage architecture that separates storage software from its hardware. Unlike traditional network-attached storage (NAS) or storage area network (SAN) systems, SDS is generally designed to perform on any industry-standard or x86 system, removing the software’s dependence on proprietary hardware.” (RedHat)
SDS uses software-based policies and rules to grow and protect storage attached to applications.
SDS allows you to use server-based storage products to add management, protection, and better usage.
Hyperconverged storage uses virtualization and software-defined storage to combine the storage, compute, and network resources along with a hypervisor into one appliance.
Hyperconverged storage can scale out by adding more nodes or appliances, but scaling up, or adding more resources to each appliance, can have limitations. There is flexibility as hyperconverged storage can work with most network and compute manufacturers.