Data Center Storage Introduction

Data center storage, a part of data center architecture, is a collective term for the devices, software technologies, and processes that design, manage and monitor data storage within a data center.

Apart from the devices and software technologies, data center storage also includes the policies and procedures used to govern the process of data storage and retrieval, for example, data storage security, data collection, data availability, and so on. Besides, data center storage must abide by the government laws and regulations related to data storage and security under some circumstances.

Types of Data Center Storage

With the advancement of information technologies, companies are provided with a variety of options on data center storage, such as solid-state drives (SSDs), cloud storage, software-defined storage, etc. However, many data centers still rely on three traditional ways of data center storage: direct-attached storage, network-attached storage, and storage area network. The three types of data center storage and their pros and cons will be discussed thoroughly below.

Direct Attached Storage (DAS)

Direct attached storage (DAS) typically refers to hard disk drives (HDDs) or solid-state drives (SSDs) and is the most common type of data center storage. Just as its name shows, DAS is attached directly to a host server, instead of connecting through a network, like Ethernet.

Besides, DAS usually connects to a computer through Small Computer System Interface (SCSI). Whether connected to a computer internally or externally, DAS is controlled by the host computer.

Advantages of DAS:

Cost-saving: DAS is much cheaper than other storage technologies, such as NAS and SAN. And the price per GB for these types of storage devices is very low, which continues to trend downward. Because of this, it is more popular in small-to-medium-sized businesses.
Better performance: Compared with other networked storage solutions, DAS cannot be affected by network bottlenecks, such as network congestion. Therefore, the data hosted on DAS can be accessed without hindrance.

Disadvantages of DAS:

Limited scalability: Because the overall configuration is too simple, DAS is easily influenced by the server. A server can only support a few expansion slots or external ports. Besides, if the server fails, the data cannot be accessed.
Not shareable enough: Since data on DAS cannot be connected through the internet, data sharing can be a big problem. If the users want to share data with someone, they have to do this through each other's computer or find another way out.

Network Attached Storage (NAS)

Network Attached Storage (NAS) is a file-level data center storage device that supports multiple users to retrieve data from centralized disk capacity over a TCP/IP network. It usually has its node on the local area network (LAN), without the intervention of the application server, allowing users to access data on the network.

As a dedicated data storage server, NAS includes storage devices (such as disk arrays, CD/DVD drivers) and embedded system software, supporting cross-platform file sharing. Besides, it also supports a variety of protocols, including Network File System (NFS), Common Internet File System (CIFS), File Transfer Protocol (FTP), Hyper Text Transfer Protocol (HTTP), etc.

Advantages of NAS:

High-efficient file sharing: NAS enables users and applications to access and edit the files on the same hard drive easily through the network, which improves the efficiency of work a lot.
Easy deployment and operation: NAS can provide reliable file-level data consolidation since file locking is handled by the device itself. It can also distribute NAS hosts and other devices across an enterprise's network environment.

Disadvantages of NAS:

Poor performance: Shared network bandwidth is a major problem limiting NAS performance. The storage data is transmitted through the network, so it is vulnerable to other traffics on the network. When there is other large data traffic, the system performance will be affected seriously.
Lack of scalability: The scalability of NAS is limited by the size of the device. Since NAS devices usually have unique network identifiers, the expansion of storage space is limited. It can only provide file storage space and cannot fully meet the requirements of database applications.

Storage Area Network (SAN)

Storage Area Network (SAN) is a dedicated and high-speed network established for storage that is independent of the TCP/IP network. It connects servers to their logical disk units (LUNs) and provides block-level network access to data center storage.

SAN typically adopts a high-end RAID array, which makes the performance of SAN stand out among other data center storage solutions. At present, the common SAN includes FC-SAN and IP-SAN.FC-SAN forwards SCSI protocol through Fibre Channel protocol, while IP-SAN forwards SCSI protocol through TCP protocol.

Advantages of SAN:

High scalability: SAN can accommodate more than 1000 devices, therefore it is very convenient for companies to increase the devices according to their needs. Besides, it includes centralized management and disaster recovery, improving storage resource utilization.
High security: SAN includes a variety of security measures to ensure data center security. For example, there are restrictions on the users who can have access to data center storage, which avoids data theft to some extent.

Disadvantages of SAN:

High cost: Not only are the components of SAN pricey, such as the high-performance hardware but there are also significant costs associated with managing and maintaining a SAN. In addition, if companies choose to use SAN, they need to pay high training expenses for IT staff.
Complex and difficult installation: SAN is complex in nature because of the sophisticated storage devices. Therefore, specialized skills and knowledge are required to maintain and deploy the SAN.

How to Choose Suitable Data Center Storage?

For a long time, choosing a suitable data center storage type has been a big concern for companies. All the data center storage types mentioned above have their merits and demerits, so the company can choose a suitable one based on the scalability, performance, IT staff, and usage case.

Scalability: The scalability of data center storage is an important element that influences the business. Compared with NAS and SAN, DAS has very limited scalability. Before making a decision, companies need to investigate the amount of data to store according to their requirements.
Performance: Whether data center storage has a good performance or not affects the company's choices a lot. Then NAS is not a good choice if the company takes the performance of data center storage seriously.
IT staff: Some companies may prefer data center storage which is easy to manage and deploy. Due to the complexity of SANs, professional IF staff is required to maintain the device, which can be a burden for some companies.
Usage case: Because of its low price and limited IT resources, DAS is more suitable for small-to-medium-sized businesses. For those larger enterprises looking for better performance and scalability, NAS and SAN can better meet their needs.

In addition to these three options, companies can also combine different data center storage types. All in all, companies should choose data center storage carefully based on their real requirements.

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