is anyone able to explain the difference between
in some articles they say users can access folders as if they were located locally in their machines. I think when you map a drive for a user it can also access folders transparently as if they were installed locally.


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joachim.claeys@teleatlas.comConnect With a Mentor Commented:
Basically NFS and CIFS are both client/server protocols
NAS and SAN are terms that define network devices

Very simply and generally said:
NFS is the most commonly used way of sharing files amongst UNIX servers
CIFS is the most commonly used way of sharing files amongst Windows server
NAS is a network device that consists of storage that is made available to server over the network
SAN is a network device that consists of storage that is directly attached to the server

Now for the full theory:

1) NFS
The Network File System (NFS) is a client/server application that lets a computer user view and optionally store and update file on a remote computer as though they were on the user's own computer. The user's system needs to have an NFS client and the other computer needs the NFS server. Both of them require that you also have TCP/IP installed since the NFS server and client use TCP/IP as the program that sends the files and updates back and forth. (However, the User Datagram Protocol, UDP, which comes with TCP/IP, is used instead of TCP with earlier versions of NFS.)
NFS was developed by Sun Microsystems and has been designated a file server standard. Its protocol uses the Remote Procedure Call (RPC) method of communication between computers. You can install NFS on Windows 95 and some other operating systems using products like Sun's Solstice Network Client.

Using NFS, the user or a system administrator can mount all or a portion of a file system (which is a portion of the hierarchical tree in any file directory and subdirectory, including the one you find on your PC or Mac). The portion of your file system that is mounted (designated as accessible) can be accessed with whatever privileges go with your access to each file (read-only or read-write).

2) NAS
Network-attached storage (NAS) is hard disk storage that is set up with its own network address rather than being attached to the department computer that is serving applications to a network's workstation users. By removing storage access and its management from the department server, both application programming and files can be served faster because they are not competing for the same processor resources. The network-attached storage device is attached to a local area network (typically, an Ethernet network) and assigned an IP address. File requests are mapped by the main server to the NAS file server.
Network-attached storage consists of hard disk storage, including multi-disk RAID systems, and software for configuring and mapping file locations to the network-attached device. Network-attached storage can be a step toward and included as part of a more sophisticated storage system known as a storage area network (SAN).

NAS software can usually handle a number of network protocols, including Microsoft's Internetwork Packet Exchange and NetBEUI, Novell's Netware Internetwork Packet Exchange, and Sun Microsystems' Network File System. Configuration, including the setting of user access priorities, is usually possible using a Web browser.

3) SAN
A storage area network (SAN) is a high-speed special-purpose network (or subnetwork) that interconnects different kinds of data storage devices with associated data servers on behalf of a larger network of users. Typically, a storage area network is part of the overall network of computing resources for an enterprise. A storage area network is usually clustered in close proximity to other computing resources such as IBM z990 mainframes but may also extend to remote locations for backup and archival storage, using wide area network carrier technologies such as ATM or SONET .
A storage area network can use existing communication technology such as IBM's optical fiber ESCON or it may use the newer Fibre Channel technology. Some SAN system integrators liken it to the common storage bus (flow of data) in a personal computer that is shared by different kinds of storage devices such as a hard disk or a CD-ROM player.

SANs support disk mirroring, backup and restore, archival and retrieval of archived data, data migration from one storage device to another, and the sharing of data among different servers in a network. SANs can incorporate subnetworks with network-attached storage (NAS) systems.

Common Internet File System (CIFS) is a proposed standard protocol that lets programs make requests for files and services on remote computers on the Internet. CIFS uses the client/server programming model. A client program makes a request of a server program (usually in another computer) for access to a file or to pass a message to a program that runs in the server computer. The server takes the requested action and returns a response. CIFS is a public or open variation of the Server Message Block Protocol developed and used by Microsoft. The SMB Protocol is widely used in today's local area networks for server file access and printing. Like the SMB protocol, CIFS runs at a higher level than and uses the Internet's TCP/IP protocol. CIFS is viewed as a complement to the existing Internet application protocols such as the File Transfer Protocol (FTP) and the Hypertext Transfer Protocol (HTTP).
CIFS lets you:

Get access to files that are local to the server and read and write to them
Share files with other clients using special locks
Restore connections automatically in case of network failure
Use Unicode file names
In general, CIFS gives the client user better control of files than the File Transfer Protocol. It provides a potentially more direct interface to server programs than currently available through the Web browser and its use of the HTTP protocol.
(*  theory taken from )

Hope this helps.
BTW: with "SAN is a network device that consists of storage that is directly attached to the server", I mean: directly attached or attached via it's own private network ( = storage area network ).
Rob WilliamsCommented:
Nicely explained but please also provide links to text used from other sites to protect EE from copyright infringements:,,sid1_gci214121,00.html,,sid5_gci214410,00.html
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At the bottom of the "theory" text, I mention "". Maybe you had overlooked it.
Rob WilliamsCommented:
Very sorry, yes, I did miss that. As mentioned, nicely explained, and it is common and quite acceptable to pull info from other sites, but though I should point out "the rules" where you are relatively new to the forum. Obviously you are aware. Guess I didn't get to the very bottom. The links I saw were from all different sites, so I assumed they were missing, they must be all linked from
Again I apologize, and I appreciate your tactful " Maybe you had overlooked it." <G>.
lepiafConnect With a Mentor Commented:
that overview is excellent, yet you could very simply put it in a few words:

NAS = file server that serves data over File based protocols, like SMB/CIFS (Win native), NFS (UNIX native), ftp, http etc.

SAN = file server that serves data as Logical Units (LUN's) via Block based protocols (FCP, FCIP, iSCSI etc.). In this case you actually send SCSI commands over either Fibre Channel or Ethernet, tunneled through TCP/IP or FCP.

The main difference is that a NAS server actually administers the data filesystem, logical volumes etc.

A SAN storage controller simply serves LUN's, which are "mounted" on Win or Sun box (or whatever else) and treated as if they were local disks, so formatting, partitioning and administering the filesystem happens on the SAN client host.

jskfanAuthor Commented:
I don't understand when they say with SAN and/or NAS  clients can see the drives as they were local disks.

I guess any mapped drive will look as a local drive to the user.
Unless if the meaning here is that user can format/partion(if the user has rights) the same way he can do for the local drives.

Regarding NAS and SAN , the only difference I can see is the speed. is there anything else?
Generally, with a SAN device, you will need the required hardware to be able to access it ( a hostbus adapter or HBA, ATM card, ... ) .  On a SAN, the storage will be seen as "local" storage to your OS, because it is physically attached.
Maximum throughput depends on the technology used to connect, but is generally faster than a NAS

With a NAS device, you would typically only need a generic network interface to be able to access your files. Typically your server will look at the storage as being "network" storage ( CIFS / NFS ) e.g. A network mapped drive in the case of Windows or an NFS share in the case of UNIX, Linux based systems.
Depending on your network speed, it's bound to be slower than a SAN.

jskfanAuthor Commented:
<<<<On a SAN, the storage will be seen as "local" storage to your OS, because it is physically attached>>>>>
there should be a wire (FC) running from the server to disk storage, and it should be the same for NAS that has a wire to run from the server to disk storage.
Can you clear it up?

the difference is the way you use the disk:

for SAN, using iSCSI, you can actually use standard GE NIC's, no HBA or so required. When "mounting" a disk in a SAN environment, it appears as locally attached, meaning as if it was hooked up to the SCSI controller of your motherboard. There's no permissions at this level, it is raw disk space that you can format as whatever you want and even partition. This is mainly used for business applications, ERP's, CRM's etc. because of reliability, multipathing, redundancy etc.

NAS is what you want to use in order to manage shares and their data from a sinlge point. The filesystem, formatting etc. is up to the NAS file server in this case, so it is quite different indeed.

hope this helps,

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