- A NAS is a Dedicated File Server Device - Clix
A Network Attached Storage device (NAS) is a hard disk with a network connection. To other computers on the network, it looks like a standard shared folder or drive. They are equivalent to a PC or server sharing out its hard disk, but in a small package and without a keyboard or monitor (setup and configuration is done through a web interface).
They can be used at home as a media server, as a corporate departmental server, or as the main file server in a small enterprise. They aren't as easy to install and configure as USB hard disks. Some technical knowledge is required.
Popular brands of NAS include Netgear, QNAP, Iomega/EMC, Western Digital, HP, LaCie, Seagate/Maxtor, Sun, Icy Box and Infrant. Warranties range from one to three years. For the network connection, the main choices are 100 megabits/sec and 1 gigabit/sec Ethernet.
NAS File Sharing Protocols
Different file sharing protocols are available. It is important that the NAS supports the right protocol:
- SMB/CIFS for Windows PCs.
- NFS for Unix/Linux computers.
- AFP for Apple Macintosh computers.
- UPnP/DLNA for use as a media server with an X-Box, PS3, i-Tunes client or Media Center PC.
Unix and Apple computers can use SMB/CIFS file shares too, though some characters such as "\" can cause problems for SMB/CIFS but are allowed as names in other systems. Apple users will also want to check that the NAS is compatible with the OS X Time Machine backup software.
Enterprises that use Microsoft Active Directory (AD) will want a NAS that can join an AD domain.
NAS Enclosures and USB Adapters
There are three main types of NAS:
- Complete NAS hardware systems, consisting of hard disks and an enclosure. The enclosure includes all the necessary electronics, and contains one to four hard disks. These are the most convenient but can cost more. The hard disks are usually standard IDE/ATA/PATA or SATA disks, but some systems use proprietary interfaces and the disks are not user-replaceable.
- NAS enclosures sold without hard disks. These are about the same as complete NAS systems, only without disks. They usually cost a few hundred dollars. Hard disks are purchased separately, usually with IDE or SATA interfaces, sometimes SCSI. The NAS enclosure should come with a list of compatible hard disks. Not all IDE or SATA disks are guaranteed to be compatible.
- USB dongles with an RJ45 Ethernet port, that convert a USB hard disk to a NAS. Brands include Addonics and Cisco-Linksys. They can cost as little as $50.
NAS and RAID
Enclosures with two or more hard disk bays are usually RAID systems. The RAID electronics combine a few physical hard disks into one logical disk. The whole NAS looks like one network drive to the rest of the network. A main data drive should be RAID 1 or 5 for reliability. If the NAS is used for data backup, reliability is less important and RAID 0 can be used. RAID 0 is also good for backup because file writes are faster.
Reconfiguring the NAS from one type of RAID to another typically erases the data, but some smart NAS can keep the data intact. Netgear's proprietary X-RAID is a RAID 1 system that allows the hard disks to be replaced by higher capacity hard disks, without losing any data.
NAS Features
Some useful features to look out for are:
- Choice between DHCP or static IP address.
- Automatic no-activity sleep mode to save power and reduce disk wear.
- Network printing to attached USB printer.
- Email notifications of disk full and other warnings (needs access to SMTP server).
- Ability to automatically shut down if notified by UPS power unit.
- Built-in ftp and web server.
- Ability to store large files (bigger than 2 or 4 gigabytes).
- USB ports for additional hard disks. These are usually mounted as separate network drives (not part of the RAID array) or used to backup data from the NAS.
- Built-in backup utility for automatic scheduled backups from PC to NAS, NAS to another network drive, or NAS to attached USB drive.
- Ability to handle Unicode file names.
- Journaling file system to handle unexpected power shutdowns without corrupting files.
- Bittorrent client, for long downloads without needing a PC.
- Ability to create users and groups, and to set access permissions (read only, read and write, no access) and login passwords.
NAS Versus File Servers
NAS functionality is equivalent to a PC or server with a shared drive. Today's small and cheap netbooks coupled with a large external drive (RAID enclosures are available, without the NAS functionality), are a good alternative to a NAS. A NAS is still attractive where space is limited. There's also one less computer to patch and maintain against viruses.
For more information on RAID, a Sun blog has information on RAID 1 versus RAID 5 read and write speeds. The Amazon website has a list of different types of NAS from various manufacturers, and informative user reviews.
Yuen Kit Mun - Kit Mun is a self-confessed information junkie, reading an average of a book a week over the past two decades. His growing Internet ...
