Now, we can also create file system on server operating system for
block level storage, so what is the advantage of using file level
access with NAS.
- You are not limiting yourself to cluster aware file systems, which are few and with their own problems (the problem in iteself is complex).
- A NAS has security on file level which is pretty important for any business level file access. In a SAN you can do that on the disc level, but every machine can read the whole disc, which means you can do a disc level analysis. A NAS can regulate access on the network interface efficiently.
That pretty much is it. Generally SAN is used for
- Single computer access (remoet boot to a volume without discs internally)
- Backend storage (no USER goes there, only computers)
A NAS on the other hand
- Is used for variety user access as it has better security (can filter out files people are not allowed to see) in one file system.
Technically there is not a lot different. Many SAN can serve as NAS, pretty much every NAS can also work as SAN. There is no hardware that is required for a SAN - many people think SAN is Fibre Channel controllers. THat is "old tech". Yes, theey are dominant, but they are not particularly fast either. 10G, Infiniband are better (particularly infiniband) when you can use them. This really these days is more a logical separation.
THe most important thing in many cases is the trust boundary. Even with cluster file systems - it would be utterly stupid to hand out files via a SAN when every computer can see the WHOLE SHARED DISC and then download it and try to decrypt the file system. A NAS has a defined safe api here - you ask for a file, if the NAS says it is not there, you can not access the disc to bypass this.