Network-Attached Storage (NAS) is the concept of a centralized data repository for storing and retrieving data on a network. NAS servers provide enhanced data storage resources, such as multiple hard disks on a computer designed for dedicated and high-performance file sharing.
This ReferencePoint describes the features of a NAS server and examines the criteria for choosing the right NAS server for your network. It also discusses the features of several NAS servers that are currently available.
Introducing NAS Servers
A NAS server is a single, large data repository that can be attached to a network. It enables you to store and retrieve files across a network, irrespective of the platform or protocol used. For example, NAS communicates with UNIX environment by using Network File Systems (NFS). NAS servers use the Common Internet File System (CIFS) to communicate with operating systems in a Windows environment. NAS also supports File Transfer Protocol (FTP) to transfer files over a network and HyperText Transfer Protocol (HTTP) to access Web pages. In addition, NAS servers perform the functions of a Web cache and provide faster access to frequently accessed Web sites. NAS also acts as a proxy server for distributed Internet connection and acts like a firewall to maintain network security.
| Note | NFS is a remote file-sharing and device-sharing protocol. It enables the end users on a network using multiple operating systems to access data stored in client computers. CIFS is a protocol suite used by Microsoft for sharing files on the network. |
A NAS server is self-reliant because it works on built-in operating systems, such as Windows, Novell Netware, UNIX, or Linux. NAS servers provide hard disks for data storage and tape drives for backups. These servers do not support peripherals such as keyboards and monitors for direct user interaction. You can use a Web browser to configure NAS servers on any authorized client computer on the network. NAS servers also enhance network security by authenticating clients and managing file services with network protocols such as NFS and CIFS.
NAS Filer
A NAS Filer is a device that is used exclusively for file storage and managing file services. NAS Filer functions as a dedicated file server on a network. The primary advantage of a Filer is that it takes over the file management operations performed by other file servers on the network. This reduces the load on these servers and enhances their performance.
Criteria for Choosing NAS Servers
Select a NAS server for your network based on your requirements, using the following criteria as a checklist:
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Installation
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Security
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File sharing
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Backup policy
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Temporary storage
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Compatibility
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Reliability
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Performance
Installation
The installation process of a NAS server should be simple. The NAS server should integrate faultlessly with the network without affecting other network components. You should be able to install the NAS server without disconnecting from the network. This ensures access to files even during installation. NAS servers should support their own operating system. As a result, you need not use additional client or server software during installation.
Security
NAS servers should provide data security by authenticating clients and managing file services with network protocols, such as NFS and CIFS. It should be possible to configure NAS servers to provide clients with read and write access rights based on their requirements.
File Sharing
Efficient file sharing is an important requirement for networks consisting of multiple operating systems running on multiple computers. NAS servers should provide support for multiple protocols that enable cross-platform file sharing. A network of diverse platforms has different types of files on each platform. A NAS server should be capable of storing these files without any conflict, irrespective of the platform on which the client-computers work. You can select a NAS server that is preconfigured to support multiple network protocols.
Backup Policy
NAS servers should provide reliable storage devices, such as tape drives for data backup. In addition to tape drives, NAS servers may also support Small Computer System Interface (SCSI) ports for dedicated backup functions. NAS servers should be compatible with several backup applications on the network, such as BackupExec.
| Note | SCSI is a high-speed parallel interface that connects hard disk drives and printers. It is defined and developed by American National Standards Institute (ANSI). |
Temporary Storage
NAS servers should serve as temporary storage devices. For example, when a file server is offline because of maintenance, a NAS server should perform the functions of a scratch server on the network. A NAS server should be able to store large volume of data. It should also be easy to transport and install the NAS server at another location.
| Note | A scratch server is used for temporary storage on a network. It is used when an application server or a file server is made offline. |
Compatibility
The time it takes to implement a new NAS server on an existing network depends on the compatibility of the NAS server with the network. An existing network may consist of multiple operating systems and protocols and files supported by these operating systems. The NAS server should be able to receive requests from client computers and respond to them over a network. To perform these activities, NAS servers should be capable of receiving an automatic Internet Protocol assignment. It should also verify whether the server replies to Dynamic Host Configuration Protocol (DHCP), Bootstrap Protocol, or Reverse Address Resolution Protocol (RARP).
| Note | DHCP is a TCP/IP protocol that assigns a temporary address to a computer on a network when it connects to the Internet. The Bootstrap protocol belongs to the TCP/IP protocol suite. It sets the host configuration dynamically at boot time. It also assigns an IP address to the host and detects the IP address of the server on the network. RARP is a TCP/IP protocol that retrieves the IP address of a computer connected to the Internet. It retrieves the IP address of the computer only when its physical address is available. |
Reliability
NAS servers should contain a reliable operating system. The operating system in NAS servers should ensure consistent performance by preventing intermittent breakdowns. They should also provide efficient data access features even during heavy network traffic.
NAS servers should also provide reliability by supporting multiple hard disk drives within the server. This process is known as Redundant Array of Independent Disks (RAID). The distribution of data across hard disks safeguards data from damage or loss.
RAID provides security to data stored in hard disks. In RAID 1 level, there are at least two disk drives with one functioning as a mirror of the other. This prevents data loss even if one hard disk fails. In RAID level 3, data is striped across an array of disk drives. This ensures effective retrieval of data. In this level, one drive is dedicated to parity. The use of parity ensures data integrity during the transfer of data from the hard disk to memory. The RAID 5 level stripes data across multiple disk drives with distributed parity. This is the safest level in data protection.
| Note | Striping is the process of performing data input and output from multiple hard disks simultaneously to increase performance. |
Performance
NAS servers should provide higher performance than application servers and file servers. A NAS server is a dedicated or single purpose server used only for file sharing on a network. The performance of a NAS server is based on the number of concurrent users it can support. A NAS server that supports advanced disk configurations such as RAID provides enhanced performance because two or more hard disks are combined to work as a single large volume disk with data striped across the hard disks.
Processor speed and memory do not alter the performance of a NAS server significantly because NAS servers are used only for file sharing.
Classification of NAS Servers
NAS servers are classified based on their ability to manage data on networks of various sizes and traffic volumes. There are three types of NAS servers:
- Low-end: These servers are designed to meet small business requirements. The storage capacity of a low-end NAS server ranges from 200 Gigabyte (GB) to 2 Terabyte (TB). These NAS servers are generally rack-mounted with four disks in each rack. The disks used are mainly Advanced Technology Attachment (ATA) or Enhanced Integrated Drive Electronics (EIDE) devices. Some of the popular low-end NAS servers are Dell 715N, Maxtor MaxAttach 4000 series, and Inline Corporation FileStorm NA 2000 Series.
Note EIDE is a hardware interface standard developed for disk drives. It supports hard disks up to 8.4 GB of storage space. ATA is the official name for disk drive interface standard defined by ANSI. - Midrange: These servers are designed for larger companies with networked branches. The storage capacity of the midrange NAS servers can be up to 10 TB. These servers are equipped with multiple processors for faster data transaction. They support RAID 1 and RAID 5 levels to provide enhanced data protection. Some of the popular midrange NAS servers are IP4700 from EMC and FileStorm NA 4000 Series from Inline Corporation.
- High-end: These servers are designed for large and data-intensive networks. The advantages of these NAS servers are large disk space that can be up to 20 TB and improved performance resulting from advanced disk configurations such as RAID 5. The operating systems built into these NAS servers contain enhanced scalability features, such as support for multiple processors. Some popular high-end NAS servers are the Network Appliance F800 family and Inline Corporation FileStorm NA 8000 Series.
Vendors of NAS Servers
NAS servers have become an alternative to file servers for file storage purposes because of the increased file storage capacity, reliability, and performance. Some of the popular vendors of NAS servers are Dell, Iomega, and Kintronics.
Dell NAS Servers
Dell PowerVault NAS servers increase the file storage capacity in small and medium networks.
A PowerVault NAS server is compatible with Windows, Macintosh, Unix/Linux, and Novell NetWare servers. This enables end users to store and share files within this single data repository. These NAS servers can also function as scratch servers besides providing backup solutions such as tape drives. PowerVault NAS servers run on Microsoft Windows 2000 Advanced server operating system. The services and utilities provided by this operating system are:
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Active Directory services (ADS): Stores and distributes information about the computers, printers, and users on a network. ADS ensures network security through logon authentication and access control.
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Persistent Storage Manager (PSM): Enhances data protection by making frequent copies of network data, which enables you to recover corrupted data during a virus attack.
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Distributed file system (Dfs) service: Is a file management system that manages files distributed across multiple computers on a network.
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File Replication Service (FRS): Replicate files on computers. This enhances file sharing by providing duplicate files to the clients simultaneously. FRS replicates even small changes made in the file.
PowerVault NAS servers are also cost-effective because the operating systems in these NAS servers impose no license fee on clients unlike the operating systems, such as Novell Netware, in file servers and application servers.
You can manage PowerVault storage servers using Web browsers.
Table 7-2-1 lists system requirements for the entry-level storage servers of different sizes:
| Storage Size | Processor | Chip set | Memory | Disk Drive |
|---|---|---|---|---|
| 160 GB | Intel Celeron@850 MHz, Level 1 Cache of 32 KB, Level 2 Cache of 128 KB transfer cache | VIA Pro133 A/T | 384 MB of SDRAM | 40 GB IDE hard disk drives |
| 320 GB | Intel Pentium III@1 GHz, Level 1 Cache of 32 KB, Level 2 Cache of 256 KB On-Die | VIA Pro133 A/T | 384 MB of SDRAM | 80 GB IDE hard disk drives |
| 480 GB | Intel Pentium III@1 GHz, Level 1 Cache of 32 KB, Level 2 Cache of 256 KB On-Die | VIA Pro133 A/T | 512 MB of SDRAM | 120 GB IDE hard disk drives |
Features of Dell NAS Servers
The Dell NAS servers have several features:
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Support RAID levels 0, 1, and 5, which provide security and performance. They also help meet the storage requirements of a network and ensure data retrieval any time without data loss.
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Secure storage of sensitive information by providing access based on the access rights of users.
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Provide configuration options that alert you to reconfigure the server when errors occur.
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Offers flexibility in terms of location because you can set it up anywhere in the workgroup. The RJ-45 connector, which connects the network cable with the network interface card on the NAS server, is used to set up these servers on an existing Ethernet network.
Table 7-2-2 lists various PowerVault NAS servers:
| Server Model | Drive Capacity | Network Connection |
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| 438 GB to 8.6 TB with SCSI and over 20 TB with fiber channel | Via Embedded Gigabit Ethernet NIC | |
| Models with 160 GB, 240 GB, and 480 GB capacity | 10/100 Fast Ethernet support | |
| 219 GB to 8.6 TB with SCSI and over 20 TB with fiber channel | Dual embedded gigabit Ethernet NICs | |
| 438 GB to 8.6 TB | Gigabit and Dual-Channel 10/100 options | |
| Dell / EMC IP4700 | 730 GB to 7.3 TB | Gigabit and Dual-Channel |
Iomega NAS Servers
An Iomega NAS server provides increased disk storage capacity up to 720 GB. It supports a multiplatform network to share and store files. This provides an effective network storage solution. Iomega NAS servers run on Microsoft Windows 2000 Advanced server operating system that provides ADS and Dfs support. Iomega NAS servers provide PSM for data snapshot and recovery.
| Note | Snapshot is a technology that retrieves corrupt or lost data. PSM stores copies of data at predefined intervals based on which the recovery is performed. |
Iomega servers are easy to install and simple to maintain because they provide plug-and-play support. Iomega NAS servers also provide SCSI ports for automatic data backup.
Table 7-2-3 lists the features of commonly used Iomega NAS server models:
| Server Model | Drive Capacity | File Protection | Operating System Used | Hard Disk | Network Connection |
|---|---|---|---|---|---|
| A300u | 120 GB | RAID 0, 1, 5 | UNIX | Three 40 GB Fast Ultra ATA-100 | Via 10/100 auto-sensing Ethernet |
| P410m | 480 GB | RAID 0, 1, 5 | Microsoft Windows 2000 SAK | Four 120 GB Fast Ultra ATA-100 Front-Load Removable | Via Dual 10/100 auto-sensing Ethernet |
| P410u | 480 GB | RAID 0, 1, 5, 5 +Hot Spare file protection | UNIX | Four 120 GB Fast Ultra ATA-100 Front-Load Removable | Via Dual 10/100 auto-sensing Ethernet |
| P405m | 320 GB | RAID 0, 1, 5 | Microsoft Windows 2000 SAK | Four 80 GB Fast Ultra ATA-100 Front-Load Removable | Via Dual 10/100 auto-sensing Ethernet |
| P405u | 320 GB | RAID 0, 1, 5, 5 +Hot Spare | UNIX | Four 80 GB Fast Ultra ATA-100 Front-Load Removable | Via Dual 10/100 auto-sensing Ethernet |
| P400m | 160 GB | RAID 0, 1, 5 | Microsoft Windows 2000 SAK | Four 40 GB Fast Ultra ATA-100 Front-Load Removable | Via Dual 10/100 auto-sensing Ethernet |
| P400u | 160 GB | RAID 0, 1, 5, 5 +Hot Spare | UNIX | Four 40 GB Fast Ultra ATA-100 Front-Load Removable | Via Dual 10/100 auto-sensing Ethernet |
Several other features that help Iomega NAS servers generate storage solutions with increased capacity and availability are:
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Support for RAID 0, 1, and 5 levels: These levels provide secure data storage and ensure data retrieval without data loss.
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Redundant load balancing: The process of distributing client requests evenly across the physical resources of the computer, such as hard disks, for efficient data availability.
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Fail-over protection: The process where a temporary replacement takes over the function of a component, such a processor or disk drive. The availability of the replacement ensures uninterrupted availability of data.
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Spare hot-swappable hard disk drives: You can replace a damaged hard disk drive on a NAS server without disconnecting the NAS server from the network. The data in the damaged disk drive will be automatically restored to the new disk drive.
Kintronics NAS Servers
Kintronics provides the FileZerver and Axis Storpoint NAS100 NAS servers. These servers are integrated network storage devices with hard disks and a modular thin server built into a tower cabinet.
| Note | A thin server contains limited software and hardware required for a specific function, such as file sharing or printing. |
The FileZerver can support 15 SCSI drives and 4 EIDE drives and Axis Storpoint can support 15 SCSI drives. Kintronics NAS servers support Windows, UNIX/Linux, Novell NetWare, and Macintosh platforms to share and store data files on a network. These servers enable you to increase hard disk space by 1000 GB or more without affecting network availability. The storage device is independent of the file server on the network. Therefore, data access is possible from anywhere on the network. These servers provide solutions for backup of data and local databases.
No installation process is required because these servers follow the Plug and Play pattern. You can configure the NAS server with the help of a quick installation wizard using a Web browser on a remote client computer. File sharing is not disrupted even when the application server is disconnected from the network.
Features
The NAS servers provided by Kintronics have several features.
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Easy installation and management: The installation process consists of two steps, plugging in the Ethernet cable and switching on the power supply. You can use a wizard and a Web browser for installation.
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Unlimited sharing: Logical drives of the NAS server can be mapped to the client computers on the network. The NAS server can support a large number of clients simultaneously without slowing down the network.
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Support for tape backup: These NAS servers provide support for SCSI and EIDE tape drives for backup.
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RAID level supports: These servers support RAID 0, RAID 1, and RAID 5 levels to enhance data protection.
Table 7-2-4 lists some of the Kintronics NAS server models:
| Server Model | Drive Capacity | Number of Hard Disk Drives Used | Hard Disk Drive Type |
|---|---|---|---|
| 1022 GB | 15 | 73 GB (hot-swap, SCSI, 2-rack) | |
| 216 GB | 7 | 36 GB (hot-swap, SCSI, tower) | |
| 180 GB | 5 | 36 GB SCSI | |
| 438 GB | 7 | 73 GB (hot-swap, SCSI, rack) | |
| 108 GB | 3 | 36 GB SCSI | |
| 72 GB | 5 | 18 GB (hot-swap, SCSI, tower) | |
| 292 GB | 5 | 73 GB (hot-swap, SCSI, rack) | |
| 144 GB | 4 | 36 GB SCSI | |
| 80 GB | 1 | 80 GB EIDE | |
| 27 GB | 1 | 27 GB EIDE | |
| 18 GB | 1 | 18 GB SCSI | |
| 72 GB | 2 | 36 GB SCSI | |
| 27 GB | 4 | 9 GB (hot swap SCSI) |
Windows-Based NAS Servers
Windows-based NAS servers are dedicated file servers that operate on Windows 2000 platform and supports Dfs, FRS, and ADS. It also performs multiplatform client support on a network to store and retrieve files.
Windows-based NAS servers provide the following features to prevent data corruption or loss:
- Disk certification: Warns against using drives not tested for compatibility. When you use an untested drive, a pop-up window warns you that the computer may become unstable.
- Dynamic system configuration: Helps avoid server downtime by helping you perform online system configuration.
- System file protection: Automatically repairs deleted or corrupted system files. This provides protection to system files.
Features
The Windows-based NAS servers have several features:
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Easy and fast installation: The installation process is easy because it supports user-friendly setup features. Installation and configuration can be performed using a Web browser from any client computer on the network.
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Easy management: The Web-based user interface helps in the management of the NAS server from a client computer on the network. This enables you to manage the servers from any remote computer on the network.
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Scalable storage capacity: Windows-based NAS servers enable you to add storage space when required. This is achieved without disrupting network availability.
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Seamless integration: These servers can be implemented in a heterogeneous environment without affecting the existing network infrastructure. This is because these servers support AppleTalk, IPX/SPX, and TCP/IP simultaneously.
Note AppleTalk is the native protocol of Apple Macintosh. Internet Packet Exchange and Sequenced Packet Exchange (IPX/SPX) is the native protocol suite of Novell Netware.
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Increased reliability: These servers use reliability features, such as disk certification, dynamic system configuration, and system file protection, provided by Windows to avoid system downtime.
- Optimized file serving: These servers provide support to protocols such as AppleTalk, Fiber Channel, and ftp, to enable multiplatform support.
Netware NAS Servers
Novell Netware NAS servers are designed to be compatible with multiplatform networks. These servers support Novell Netware, Windows, UNIX, and Linux files. Novell Netware NAS servers are built on Netware 5.1 kernel. These servers use Novell Directory Services (NDS) eDirectory to maintain user access and security.
The Novell Netware operating system is not restricted to a specific hardware configuration and is compatible with the various classifications of NAS servers. Netware NAS servers support HTTP, NFS, CIFS, NetWare Core Protocol (NCP), and FTP for file sharing.
| Note | NDS is a globally accessible, enterprise-wide database of all network resource information. NetWare use the NDS to manage network objects. |
Netware NAS servers have a simple installation process. A network manager can connect a NAS server to a network through the Ethernet port. The configuration of the NAS server can be performed from any client computer on the network using a Web browser. End users working on multiple platforms such as Unix/Linux and Windows can access these NAS servers because they support Windows Domain Controllers, Windows Workgroups, and Unix Network Information Services.
