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SAN Vs NAS


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#1 ramkumar

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Posted 27 November 2012 - 02:31 AM

Hello Team, i am new to this Forum. Hope you are well.

I have a query regarding NAS and SAN.

Can any one please provide the major differences between SAN AND NAS in a practical way. Please help with with Example without fail.

Thank you so much in advance

#2 Stoyan Varlyakov

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Posted 28 November 2012 - 06:00 AM

Hello Team, i am new to this Forum. Hope you are well.

I have a query regarding NAS and SAN.

Can any one please provide the major differences between SAN AND NAS in a practical way. Please help with with Example without fail.

Thank you so much in advance


Just take a look here:
http://www.techrepub...comparison/3766
NAS is in general file based storage
SAN is in general block based storage

Then keep on googling, a proper answer will need at least a book to explain.
What you see above is my personal opinion. Don't take it as the holy bible and the one-and-only truth :)

#3 Relax_nl

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Posted 28 November 2012 - 02:56 PM

My 2cents explanation:

NAS devices allow a client to access the storage resources using high-level file-oriented protocols like NFS,SMB/CIFS, AFP, while SAN devices allow to access the storage resources using low-level block-oriented protocols like iSCSI.

#4 ramkumar

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Posted 29 November 2012 - 06:20 AM

Hi Team,

Thanks for the post.

I need a explanation in a practical way. so that it would be easy to understand.

for example: if you attache a hard disk in a desktop machine that is cabinet. then it becomes DAS.

Can any one explain me in that way?

#5 ramkumar

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Posted 29 November 2012 - 06:35 AM

I just want to know what is file based and what is block based. i have a big confusion how file base looks and block base looks.

I need it with diagram. is that possible. please help me to understand

Edited by ramkumar, 29 November 2012 - 06:39 AM.

#6 Stoyan Varlyakov

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Posted 29 November 2012 - 06:44 AM

NAS - can be accessed by end users and devices. Provides services to share data like word files, folders and .zips
SAN - can be accessed only by devices which are capable of talking to the type of SAN, because there are many. A typical SAN client is a cluster environment.

There is no easier way to explain it, or at least I am not able to.

If you find that hard to understand, please start reading about file based storage and block based storage.
There is no quick and dirty way to become an storage expert unfortunately.
What you see above is my personal opinion. Don't take it as the holy bible and the one-and-only truth :)

#7 ramkumar

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Posted 29 November 2012 - 07:22 AM

Hello Stoyan,

thanks for post. i have read the documents regarding NAS and SAN before . But the problem is not able to gather details in a practical way.

I could understand theoretically and i would say as a storage expert theatrical knowledge is not enough to shine.

#8 ramkumar

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Posted 29 November 2012 - 07:25 AM

From my knowledge i would say that,

SAN Can able to extend the Storage Box where is NAS cannot be able to extend Storage Box.

Can any one tell me, whether SAN has inbuilt Operating system like NAS has ?

#9 Stoyan Varlyakov

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Posted 29 November 2012 - 08:16 AM

SAN can be in general anything - from JBOD units to OS Based block sharing over iSCSI, iFC etc... So it is rather difficult to answer simply.
In a pure hardware form SAN is a Network - this means many devices are concerned.
1 Device by itself cannot form a SAN.
You could build a SAN using FC, SAS, and TCP based implementations like TCP over InfiniBand, iSCSI in 1G and 10G Ethernet...

10 years ago SAN was limited to Fibre Channel
so in this form all you needed was a firmware and a SAN switch. Now however you have the so-called hybrid storage which has a SAN part (Nexenta, OpenFiler, even typical Server OS with iSCSI Target installed could be considered SAN member...) and a NAS part (Sharing files over SMB/CIFS ; NFS ; AFP ...).

The difference is that in a SAN you have a number of blocks to be accessed which then you have to control using the client to form a volume and install an file system over it, whereas in a NAS application, the Filesystem and OS should not matter - it is a different protocol which is in the base of the whole thing.
In Windows Networks the network file sharing protocol is calles System Message Block (SMB) also known as Common Internet File System (CIFS), and the linux daemon for this type of access is usually samba or smbd.

So go back to my first post - there is not a simple way to explain SAN and NAS with diagrams and examples. You have to get the whole picture to know what is the one and what is the other.
What you see above is my personal opinion. Don't take it as the holy bible and the one-and-only truth :)

#10 ramkumar

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Posted 30 November 2012 - 05:22 AM

That's really great to get this information.

and thanks for sharing the information.

And also i would say block level access is more faster compare to file level access.

Is there any opposition for this point?

#11 Stoyan Varlyakov

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Posted 30 November 2012 - 05:27 AM

...
And also i would say block level access is more faster compare to file level access.
Is there any opposition for this point?


In near perfect conditions - same switch, etc etc. Block based will have significantly lower latency, which usually means better performance.
But in large sequential access patterns, where caching can be done on many levels (OS, Application), then file based might be the better solution.

And if you are talking about geographically separated areas, then you NEED an application to deal with the latencies involved, therefore file based will be in general the better solution.
I am excluding from this generalization the proprietary enterprise solutions from EMC, NetApp etc.
What you see above is my personal opinion. Don't take it as the holy bible and the one-and-only truth :)

#12 ramkumar

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Posted 30 November 2012 - 05:51 AM

Thats correct. And thanks for sharing.

#13 ramkumar

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Posted 30 November 2012 - 05:55 AM

Once we created a LUN in SAN. for example the lun name is LUN1.

my questions is, Can LUN1 be able to attach as a drive in 2 different Servers. and the can it be able to access?
i think it wont ?

If not please provide your valuable answer.

Thank you.

#14 Stoyan Varlyakov

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Posted 30 November 2012 - 08:43 AM

Once we created a LUN in SAN. for example the lun name is LUN1.

my questions is, Can LUN1 be able to attach as a drive in 2 different Servers. and the can it be able to access?
i think it wont ?

If not please provide your valuable answer.

Thank you.


This is indeed possible, but I would want to do that only on a cluster file system OR a cluster aware application like say Microsoft Clustering Add-on.
Then you add the same LUN/DISK on many servers, but only 1 has actual access to the LUN.

Most common scenario for FS Corruption in the given example is when the hearbeat NIC goes bad/away and both nodes become active.
Instant FS Lock up/corruption.

On a large scale cluster file systems, you access the same block device with multiple nodes, but the algorithm for write locking is a very comprehensive one...

Edited by Stoyan Varlyakov, 30 November 2012 - 08:45 AM.

What you see above is my personal opinion. Don't take it as the holy bible and the one-and-only truth :)

#15 clicker666

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Posted 30 November 2012 - 01:27 PM

Stoyan - you could create a share on an iSCSI link based on the underlying file system though. (like we were talking about for my system) So he could have OpenFiler connected via iSCSI to a Windows 2003 server, and create a SMB share on that server for the workstations. The iSCSI link would be running block level from Openfiler to Server, and file level from Server to workstations? I'm not entirely sure, because I haven't had the opportunity to try yet, but I figured Stoyan might know.

#16 Stoyan Varlyakov

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Posted 03 December 2012 - 03:20 AM

Stoyan - you could create a share on an iSCSI link based on the underlying file system though. (like we were talking about for my system) So he could have OpenFiler connected via iSCSI to a Windows 2003 server, and create a SMB share on that server for the workstations. The iSCSI link would be running block level from Openfiler to Server, and file level from Server to workstations? I'm not entirely sure, because I haven't had the opportunity to try yet, but I figured Stoyan might know.

Hi Clicker,

yes that is possible.
But when you look at the setup, you have 2 separate connections:
1. Openflier to OS which is a SAN-type connection
2. OS to Clients which is NAS-type connection

So yes, of course it is possible.
But in a SAN or sometimes referred to as "storage network" you need different NIC settings - larger MTU (9000 is what is most compatible these days), TOE Options to a certain extent, Link Aggregation etc.
In an NAS environment because you usually have a large mix of clients, it is best not to fiddle with the MTU size, and disable TOE altogether, because from my professional experience it is the number 1 cause of surprisingly low network performance.

Therefore we still draw a fat red line between the both.

Just my 2 cents.
What you see above is my personal opinion. Don't take it as the holy bible and the one-and-only truth :)

#17 ramkumar

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Posted 05 December 2012 - 04:02 AM

I have a suggestion for attaching a lun with two Windows server.

If we create a LUN and attach this LUN as a Datastore in ESX.

Using 2 windows server ( that is 2 VM ) in this ESX, can the LUN be able to attach as a hard disk in these two windows server?

I am explaining this for the above qestion raised by me..

can any one please explain if is this possible or not. I have not tried it.

#18 Stoyan Varlyakov

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Posted 05 December 2012 - 04:39 AM

I have a suggestion for attaching a lun with two Windows server.

If we create a LUN and attach this LUN as a Datastore in ESX.

Using 2 windows server ( that is 2 VM ) in this ESX, can the LUN be able to attach as a hard disk in these two windows server?

I am explaining this for the above qestion raised by me..

can any one please explain if is this possible or not. I have not tried it.


This can be done, sure.
But then you need clustering in order to access the *same* portions of the hard drive (volumes, blocks, etc...) or else you will have data corruption.
What you see above is my personal opinion. Don't take it as the holy bible and the one-and-only truth :)

#19 ramkumar

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Posted 12 December 2012 - 11:55 PM

Over all which Technology is best to use ? ( SAN Or NAS )

Does SAN has internal operating system as NAS Has?

IF Yes please give ma one example in SAN

Edited by ramkumar, 13 December 2012 - 01:13 AM.

#20 Stoyan Varlyakov

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Posted 13 December 2012 - 03:46 AM

Over all which Technology is best to use ? ( SAN Or NAS )

Does SAN has internal operating system as NAS Has?

IF Yes please give ma one example in SAN


SAN vs NAS - is Servers vs Clients
If client-centric and small offices, NAS is great.
If enterprise or multi server environment SAN is a must.

SAN with OS = Nexenta; Open-E etc.

But those are customized OSes, you cannot co-exist a SAN-specialized OS with say a Web server...
What you see above is my personal opinion. Don't take it as the holy bible and the one-and-only truth :)

#21 ramkumar

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Posted 13 December 2012 - 11:56 PM

Ok I understand that OS should needed for SAN.

DO SAN have control station and data movers as NAS has? A bit confusion on this. and also would like to know what software is used for creating LUN in SAN storage.

I have Unisphere and Navisphere used in our hybrid model. But got confusion .

#22 Relax_nl

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Posted 14 March 2013 - 10:23 AM

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#23 poshhagrid

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Posted 16 April 2013 - 06:32 PM

Its very interesting, reading all this. I'm trying to learn but it pretty difficult. There's a lot of technical terms and if I'm honest, I reckon a lot of people like me just want it simple. I got confused when looking into "SAN" because I came across something about website security certificates! (www.itsolutionspeople.com) They told me its a common term across both products, as if it wasn't enough to take in!

I'm trying to help out my mom's business with a file sharing network for 14 employees. What am I going to need?

Any help would be great.

#24 clicker666

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Posted 16 April 2013 - 06:39 PM

Its very interesting, reading all this. I'm trying to learn but it pretty difficult. There's a lot of technical terms and if I'm honest, I reckon a lot of people like me just want it simple. I got confused when looking into "SAN" because I came across something about website security certificates! (www.itsolutionspeople.com) They told me its a common term across both products, as if it wasn't enough to take in!

I'm trying to help out my mom's business with a file sharing network for 14 employees. What am I going to need?

Any help would be great.


For a small network I would just use a small file server. Either Windows or some Linux distro. SAN is probably overkill, and if you don't have an expert on hand you could lose a lot of data if things go wrong. Keep it simple.

SAN is a block level device - it's a specialized box that acts like a big fast hard drive. You need a server that can connect to it. NAS is a storage device attached to your network with shares on it. (Generally) SAN would likely be a lot more expensive than NAS.

So I would build a small file server with good hard drive redundancy and a backup strategy.

#25 nani

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Posted 15 August 2013 - 09:01 PM

Ok I understand that OS should needed for SAN.

DO SAN have control station and data movers as NAS has? A bit confusion on this. and also would like to know what software is used for creating LUN in SAN storage.

I have Unisphere and Navisphere used in our hybrid model. But got confusion .





Hi,

Control station and data movers are internal part of CELERRA which is a storage box,NOT differs in NAS and SAN.when regarding to LUN
unisphere is for SYMMETRIX(storage box-high end) navisphere is for CLARIION (storage box) both are SAN storage boxes only.

First CELERRA next CLARIION next SYMMETRIX next vmx are the storage boxes manufactures by emc a mnc



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