Data Storage 101

Data Storage 101

In this guide, we will explain the differences between:

» DAS (Direct Attached Storage)

» JBOD (Just a Bunch Of Drives)

» NAS (Network Attached Storage)

» SAN (Storage Area Network)

» NAS vs SAN

» Storage Servers

» Storage Virtualization

» SDS (Software Defined Storage)

» Free storage software

We’ll also discuss when it is best to use each of these technologies.

DAS (Direct Attached Storage)

Direct Attached Storage (DAS), also called Direct Attach Storage, is

digital storage that is attached directly to a PC or a server. In other

words, DAS isn't part of a storage network.

The most familiar example of DAS is the internal hard drive in a laptop

or desktop PC.

In practice, the term "direct attached storage" is used most often in

reference to dedicated storage arrays attached directly to servers.

It is used to distinguish DAS from networked storage arrangements, like

SAN or NAS devices.

DAS (Direct Attached Storage) – cont.

DAS can refer to a single drive or a group of drives that are connected

together, as in a RAID array.

In addition, DAS devices can be housed inside a PC or server (as is the

case with internal hard drives) or outside the PC or server (as is the

case with external hard drives and JBOD’s).

The primary benefits of DAS include simplicity and low cost.

Most PCs and servers come with DAS already installed and if you want

to add more direct attached storage, generally all you need to purchase

is a storage device and possibly a cable.

DAS (Direct Attached Storage) – cont.

Installing networked storage systems, like NAS and SAN devices,

requires additional planning, as well as the purchase and deployment

of network hardware, such as routers and switches, in addition to

appropriate cabling and connections.

Maintaining DAS is very simple; by contrast, SAN and NAS solutions

usually require management software and may require monitoring

software as well.

JBOD (Just a Bunch Of Drives)

JBOD (an acronym for "just a bunch of disks," or sometimes

"just a bunch of drives") is an array of hard disks that haven't

been configured.

A JBOD chassis presents the individual disks (to a server) with no

structure applied.

The drives can be used as individual logical volumes or

configured as a RAID using a RAID card or software.

NAS (Network Attached Storage)

A NAS is a server connected to the local area network that is dedicated

to nothing more than file sharing.

NAS allows more storage space to be added to a network without

affecting any systems already on the network.

With a NAS device, storage does not need to be an integral part of the

desktop/workstation/server. Instead, the desktop/workstation/server

still handles all of the processing of data but a NAS device delivers the

data to the user.

NAS (Network Attached Storage) – cont.

A NAS device can exist anywhere in a network and many can be added

to the network infrastructure.

The advantage of NAS over DAS is that it simplifies file sharing among

multiple users.

» Example: Buffalo TeraStation

SAN (Storage Area Network) – cont.

A SAN is a high-speed network of storage devices, separate from the

local area network, that also connects those storage devices with

servers.

It provides block-level storage that can be accessed by the applications

running on any and all servers connected to the SAN.

SAN storage devices can include tape libraries, and, more commonly,

disk-based devices, like RAID hardware.

» Example: Promise Vess

NAS vs SAN

It is easy to confuse the two, but SAN (storage area network) is an

actual network, while NAS (network-attached storage) refers to a

storage device, typically in an IP (LAN) network.

While a SAN provides block-level storage for servers, a NAS device

provides file-level storage for end users.

The mail application on company servers might utilize a SAN to store all

the messages, contacts and other data it requires.

An end user would use a NAS device to save files, such as word

processing documents or spreadsheets.

NAS vs SAN – (cont.)

NAS is a much simpler and less expensive technology.

Using NAS devices actually simplifies the task of adding storage to a

network because the NAS eliminates the need to configure a network

operating system for routine file-sharing tasks.

A storage area network is designed for managing very large amounts of

network storage.

For large organizations with many servers that need access to the same

data, SAN offers better performance and flexibility than DAS or NAS.

NAS vs SAN – Summary

» Intel® Xeon® E5-2600 v3 processors

» NAS devices offer a simple, inexpensive way to get shared file-based

storage.

» NAS works across the network while SAN doesn’t. While SAN

volumes can be mapped across the network, the file sharing on a NAS

is much simpler.

» NAS can be accessed across multiple operating systems but not SAN.

Windows, Linux and Mac OS can easily see files on a NAS.

NAS vs SAN – Summary (cont.)

» NAS backups are more efficient than SAN backups. This is because

the files themselves are backed up instead of all of the blocks on the

disk.

» For maximum performance, SANs provide a stronger information

infrastructure foundation.

» There are other hybrid options available, such as iSCSI SANs, which

offer some of the best features of both worlds.

Storage Servers

A storage server is a network server that is dedicated to managing

storage. A network attached storage (NAS) device is a true storage

server because it is dedicated to data access and nothing else. This is in

contrast to a file server, database server or video server which perform

other functions besides managing storage. Storage servers tend to run

an operating system tailored to the task of managing large amounts of

storage.

» Examples: Microsoft Storage Server, Open-E

Storage Virtualization

Storage virtualization is the pooling of physical storage from multiple

network storage devices into what appears to be a single storage

device that is managed from a central console.

Storage virtualization helps the storage administrator perform the

tasks of backup, archiving and recovery more easily -- and in less time

-- by disguising the actual complexity of a SAN or cluster of NAS

devices.

Administrators can implement virtualization with software

applications or by using hardware and software hybrid appliances.

SDS (Software Defined Storage)

SDS is a storage infrastructure that is managed and automated by

software as opposed to by the storage hardware itself.

It can be thought of as a software layer that provides storage

services.

In this way, the pooled storage resources in an SDS environment can

be automatically and efficiently allocated to match the needs of any

application.

SDS (Software Defined Storage) – cont.

The key benefits of software-defined storage over traditional storage

are increased flexibility, automated management and cost efficiency.

The downside to SDS is that the server has to allocate greater

resources to manage the storage. Functions that were done in

dedicated hardware on traditional storage systems now has to be

done by the server CPU. This can impact the speed and

responsiveness of other applications running on the server.

» Example: Microsoft Storage Spaces

Free Storage Software

Eventually, you will hear the old adage “Hey, I read about this free

software, such as FreeNAS, NAS4free, OpenFiler, etc. Why can’t I use

that?”

While it may be free to acquire the software, most have the

limitation of being NAS based. Maximum available storage, security

and data integrity may also be limited. Setting up and maintaining the

system can be time consuming and require significant technical skills.

They may end up costing more in the long run than purchasing

purpose built storage systems.

Summary

» The types of storage used depends on the needs of the customer.

» Separate desktops/workstations/servers can use DAS if no other

systems need access to the data.

» NAS can be used for simple file sharing.

» SAN is used when multiple servers need access to the same data

(ex: databases).