Network attached storage is an ideal way for small offices to share and backup data. We explain what to look for when buying one of these devices.
Network attached storage (NAS) is exactly what it sounds like. Instead of connecting storage drives directly to individual computers, a NAS device creates a pool of storage that can be shared by multiple computers and other devices.
- Convenient access to shared data
- Greater reliability (some configurations can survive the complete failure of a disk drive)
- Simplified backup (a NAS can be the backup destination for multiple computers, and data stored on the NAS can be easily backed up to another location)
- Features on some NAS devices that can make it easy to access files stored on the NAS via the internet.
Furthermore, a NAS is easier to set up and manage than a general-purpose server, even when the NAS includes functions such as email and web servers.
However, choosing a NAS from the wide variety of devices available can be tough. In this first part in our NAS feature series, we explain the key things to consider when buying one.
You can buy single-bay NAS units, meaning it can contain one hard disk drive, but multiple-bay systems provide more flexibility.
The more bays there are, the greater the maximum capacity, but more importantly this allows drives to be combined in various ways that provide different balances of performance, capacity and protection from drive failures.
Other features that may prove useful are support for 'hot-swappable' drives, which allow you to replace a drive without powering down the device, and the ability to add an expansion chassis to accommodate additional drives.
You’ll see the term RAID (short for Redundant Array of Independent Disks, though RAID doesn’t always provide redundancy). There are various RAID ‘schemes’ (or types), including:
- RAID 0, which ‘stripes’ data across multiple drives to improve performance, though if one drive fails all the data is lost
- RAID 1, which ‘mirrors’, or puts the same data on, two drives, so if one drive fails there is still a complete and usable copy of the data on the other
- RAID 5, which requires at least three drives. It stripes the data and adds ‘parity data’ so that any one drive can fail without losing data – though it’s important to replace the failed drive promptly so its contents can be regenerated before another failure occurs.
- RAID 10, which combines striping and mirroring
- RAID 50, which combines striping and parity.
In general, all the drives in a RAID setup must be the same size or space will be wasted. For example, if 4TB and 6TB drives are combined, only 4TB of space will be used on the 6TB drive(s).
Choice of drives
It’s generally a good idea to follow the manufacturer’s recommendations when selecting hard drives for NAS use. Reliability is important, so don’t try to economise by installing drives that aren’t designed for this style of operation.
Some NAS devices make specific provision for solid state drives (SSDs) that are used to cache frequently used data to improve performance.
As a general rule, four, six and eight-bay units have faster processors and more RAM, so they are better able to cope with the demands of RAID, heavier use by more users, and software such as web servers, mail servers, content management systems and virtual machines.
The more data you need to get on and off the NAS, the more network bandwidth required. RAID and SSD configurations may be capable of delivering data faster than a single Gigabit Ethernet port can handle, so demanding users may need to consider models with multiple ports or provision for 10GbE.
A NAS is a convenient way of collecting and storing surveillance camera feeds. Some models provide explicit support for this, either as a standard feature or via add-on software.
You can use a connected PC to scan the contents of a NAS for malware, but that consumes a lot of network bandwidth. The job is better done on the NAS itself, where that option is available.
A common use for a NAS is to provide a single backup destination for multiple computers. If the NAS includes appropriate software, that’s one less thing you need to buy, providing the bundled licence covers the sufficient number of PCs.
The use of RAID might give you more than one copy of your data, but that doesn’t count as a backup. All it does is protect against a drive failure – it’s of no help if the unit is stolen or destroyed in a fire or flood.
There are three main ways of backing up a NAS.
- Connect an external drive and use that as a backup destination. That has several drawbacks. You’d need multiple drives in order to provide the required capacity and to maintain an offsite copy at all times. That also makes it a manual process, and as soon as people are involved in a backup process there’s more room for it to go wrong.
- NAS-to-NAS backup. Two NAS units can be connected either locally or via the Internet so the backup process is automatic and often continuous. Unless starting from scratch, it’s a good idea to do the initial backup locally to speed up the initial backup and reduce data transfer costs. Keeping both units in the same location is faster and cheaper, but doesn’t provide an offsite backup. If the destination NAS is kept in the same town or city, this approach will normally provide the fastest recovery from a catastrophic failure as you can simply drive over and pick it up.
- NAS-to-cloud. Similar to NAS-to-NAS, but the destination is a cloud storage service such as Amazon Web Services. This reduces the upfront cost and may allow you to keep more versions for longer as the available space is limited only by your budget. A complete recovery is likely to be time-consuming and relatively expensive in terms of storage and bandwidth charges.
One or more of these capabilities are often standard features of NAS units, but additional software is sometimes required. If your data is important enough to put on a NAS, it’s important enough to back up.
In addition, it’s sometimes possible to sync a NAS folder with services such as Dropbox.
Vendors often offer mobile apps to make it easy to access files from phones and tablets. For some organisations this is an attractive alternative to cloud services such as Dropbox or OneDrive.
NAS devices often include media server functionality. While this is primarily aimed at home users, it can be useful at work for playing promotional and other videos in public areas, or providing background music (subject to the necessary licences).
Other features on offer include support for virtualisation and containerisation. These are high-end features for technical types, which we explain in part three of our series. But for now, if you don't know what they are, chances are you won't need them.
In part two of our feature series, we look at a range of NAS devices that might be suitable for your business.