Server 101: SAN and NAS

Storage is one of the topics that is done differently in the corporate world than home environment. In SOHO data is usually stored in directly attached hard drives and in a device in a device over the network using a NAS. On the other side, corporate usually depend on something called a SAN to store their corporate data.


Image of a NAS
Synology DS1511+ NAS – Courtesy of Synology


NAS stands for Network Attached Storage, which is basically generally a device over the network that is used to host and share information over the network. The device can serve multiple services or dedicated for file storage.

NAS is a file level storage. File level storage mean that the NAS and the client exchange files between them over the network, just like when a file download from a website. Moreover, with file level storage files are usually stored in a fixed location with a fixed storage capacity. As a result, expanding storage capacity is usually not possible and always require some downtime.

There are many protocols used for files storage such as SMB and AFP. Most NAS devices nowadays support and use SMB as its main file exchange protocol.



A picture of a SAN Component
emc VNXe1600 SAN – Courtesy of EMC

SAN stands for Storage Area Network and it is a network of multiple devices connected to serve a single purpose …storage. The network contains fiber matrix, storage controller and even pools of blazing fast hard drives.

Unlike NAS, SAN uses block level storage. In a nutshell, block level storage means that communication between the SAN and the client is treated like a directly attached hard drive into a motherboard. As a result, SAN mounts are visible as a local hard drive on clients.

There are two main protocols for SAN: iSCSI (Internet Small Computer Systems Interface) and FC (Fibre Channel). Most SAN nowadays use FC is built specifically for SAN and it is faster than iSCSI, but it is more expensive.

Why SAN over NAS?

Large enterprises use SAN over NAS for multiple reasons. First, SAN performance is higher than most NAS devices, due to the way storage area networks are built. Second, SAN allow easily to modify storage allocation of each storage mount. Also, the mount can reside on single hard drive, single virtual hard drive and event on two different building! Third, Storage are networks are real fault tolerant if built correctly. HP has proofed that a SAN can be bullet proof literally in an old TV commercial!!! The commercial can be viewed bellow.


Hemo’s Take

It is alright if you are not very familiar with SAN, as it is considered as big boys toys. Myself, I don’t have the permission to work with it yet, but one day both of us will work with it ?

Automating Operating System Installation

Screenshot of MDT
Courtesy of Microsoft

Operating system installation is one of the most basic and simple process done by sysadmins or help-desk people, yet it is one of the most expensive processes for any business, because it wastes IT staff time and employees time. Besides being expensive and time consuming, it is also very repetitive and prone to errors.

The problem

Let’s image the following, your business decided to build an onsite training center at work with capacity of 25 trainees. The new center needs a new machine for each trainee in the center. Moreover, these machines come without an operating system, because you already have an enterprise license from Microsoft. Accomplishing this task will keep the entire team busy for the entire day!  By the end of the day, you will have a dead tired team who spent an entire day on a single task, and training team who were idling due to uninstalled machines.

The traditional way the team is doing this task is by grabbing an installation disc and fill the prompted instruction, until the end. During this process, the staff member must be next to the machine to answer the required questions. The actual process can take up to an hour per machine.

The biggest problem with operating system installation is not the time it consumes, but the IT team might have 25 machines with 25 different configurations. Such difference in configuration may lead into future problems in the future.

Such process can be enhanced by complying two main principles. First, Automating the processes as much as possible. Second, unifying all the hardware and software as much as possible. Operating system installation automation complies these principles.


In a nutshell, operating system installation is done using through running a PXE server, and creating a proper answer machine file which is used answer question asked during installation.

Available solutions

They are different solutions used for operating system automation. Microsoft suggests Microsoft Deployment Toolkit to automate their operating systems. Red Hat released Kickstart to automate its operating systems.

Hemo’s Take

Cloning is also a solution, but I suggest not to use it. The master image of the clones needs to be up to date to have all the chnages. Also, SA needs to run sysprep to change GUID and SID of each clone. Finally, cloning hides the history of the process. As a result, the SA does not know installation history.