SAN or NAS?

[WilliamsIT]

Can an application that stores data as files benefit from the performance SAN Storage? I’m looking at a few NAS appliance that can be configured as NAS device or be used with iSCSI to connect to a server as a storage device for block-level access. I want to use what will give me the best performance.

My confusion comes when you hear about SAN stoarge being block-level and NAS storage being file-level. Different articles that I read say you should SAN when using transactional databases, so does that mean you shouldn't use SAN storage if the application stores data as files?

 

[comtec17]

This will depend on a number of factors.
-Application type
-Block size
-Type of I/O (sequential, large, small)
-Number of I/O per second needed
-Bandwidth (MB/sec) needed

Fibre Channel speed can be as much as 4GB/sec while NAS can only sustain around 75MB/s on a GigE network.

The difference between file level and block level are just that. A Block device is a LUN or disk presented to the server as local storage. A file level device is a share.

Using iSCSI or Fibre Channel presents disk devices to the server, using NAS presents the disk as a share (NFS, CIFS).

 

[WilliamsIT]

Thanks for the reply and information. So that I completly understand, you can use a SAN Storage device for files, data files, and any application that needs a place to copy files? Or asked another way, you don't have to use SAN Storage (Block level) only for transactional databases application?

Massive Success

 

[comtec17]

No.

A SAN attached disk device shows up as local disk to the server. It does not matter what is on it.

 

[p5wizard]

If you need the speed of a SAN for one or more database applications, then there's really no need to invest some more money in a NAS box to host your file servers' filestores.

You present SAN LUNs to whatever servers that need storage, build one or more filesystems/partitions on the LUNs that the servers see as hard disks. Then load the filesystems with your data (ordinary files or DB files, makes no difference) and fire up your DB (and other) applications.

Note however that using a high-end SAN diskbox to host fileserver data is considered overkill by some admins (and their bosses I guess). But of course you can put different type/size of disks in the SAN diskbox to host the different type of data.


HTH,

p5wizard

 

[WilliamsIT]

Thanks guys. Not sure how I made the understanding of this topic so confusing, but I get it now.

Thanks again.