Can someone list the advantages of NAS over SAN ?

[Shivkumar]

Hi,

Can someone list the advantages of NAS over SAN ?

Thanks,
Shiv

[Uwe Zessin]

NAS is 'file serving' and SAN is 'block serving'.

Each technology has its own advantages and disadvantages - there is no single 'perfect solution' for all uses.

[Steven Clementi]

Furthermore... Some NAS heads have a SAN behind them to serve up the storage that they then serve up to the network.


A Network Attached Storage (NAS) node are generally self contained and use a DAS (Direct Attached Storage) technology while others, like the HP Proliant DL380 Storage Server, usually come with some limited amount of local storage.. but you then connect it to a MSA or an EVA or some other Storage Array to server up gobs more.

A Storage Area Network (SAN) technically refers to the infrastructure behind a storage solution, but is commonly used to describe storage arrays such as the MSA or the EVA and even the XP.


Steven

[Uwe Zessin]

Good point, Steven. NAS and SAN technologies are not enemies -
they can (and often do) work together in an environment.

[Sivakumar MJ._1]

In NAS the Backups & Mirrors (utilizing features like NetApp's Snapshots) are done on files, not blocks, for a savings in bandwidth and time. A Snapshot can be tiny compared to its source volume and in SAN it requires a block by block copy, even if blocks are empty. A mirror machine must be equal to or greater in capacity compared to the source volume.

[Jozef_Novak]

Modern NAS devices are usually able to work with a variety of protocols (including Fibre Channel) while SAN is strictly fibre-based. The usual advantage is lower cost and no need for a separate infrastructure (theoretically). However, as other have written, there is no general preference and the choice always depends on a particular environment.

J.

[Uwe Zessin · Accepted solution]

> In NAS the Backups & Mirrors (utilizing features like NetApp's Snapshots) are done on files, not blocks, for a savings in bandwidth and time.

On the low-level, both technologies work with blocks. Some SAN arrays can provide a snapshot-based replication, too.

Full-change replication like CA-EVA and snapshot-based replication are just different uses - each one has its own advantages / disadvantages.

> A Snapshot can be tiny compared to its source volume and in SAN it requires a block by block copy, even if blocks are empty.

Not true for vsnaps on the EVA, for example. I think you are confusing Snapshots with volume clones.

> A mirror machine must be equal to or greater in capacity compared to the source volume.

Not true, unless I misunderstood. On all arrays I am familiar with you can replicate a subset of the total storage ressources, so the destination system can be smaller.

[Tom Nieman]

One more thing about files vs. blocks.

Trying to simplify in case this is searched on:

Operating systems generally deal with files, where an application (like Oracle) may deal with blocks or files. Blocks used to be much better for performance and security of an application. That has been changing over time as NAS technology has matured.