After reading about File vs. Block storage at File vs. Block storage on 18.15m , looks like both both block based storages(SAN) and files based storage devices(NAS) stores the internally as block .
But at couple of other resources like https://stonefly.com/resources/what-is-file-level-storage-vs-block-level-storage and https://www.networkworld.com/article/3256312/what-is-a-san-and-how-does-it-differ-from-nas.html I see below claim
A SAN stores data at the block level, while NAS accesses data as files.
It stores files and folders and the visibility is the same to the clients accessing and to the system which stores it.
From this looks like File based storages stores the data as file(not blocks) in sequential fashion. Not sure which one is true ?
It's a matter of terminology only. On their back-ends, both types of systems store data in blocks and the difference between them is in front-end protocols they provide to a client. Block storage systems allow access via block-level protocol - in the most cases it's SCSI (SCSI over FC or SCSI over TCP/IP - iSCSI). Respectively, front-end of a file storage operates on file-level protocols: NFS, SMB/CIFS. It happens, a storage device can work in both modes: block and file.