Why Use External Storage

External storage can be used for a number of reasons, as explained in the tabs below.

Expansion

Expansion

Additional storage can be added easily by connecting an external enclosure with one or more additional drives in it. The enclosure may be temporarily or permanently connected to the computer, and used for adding to the internal storage or for protecting sensitive files if the external storage has multiple drives.

Sharing

Sharing

A network router connects devices together by ether wired connection or wireless technology. By storing data on a network connected enclosure, it allows multiple users to access it either locally or remotely. Usually Network Attached Storage (NAS) devices have multiple drives in them as the intended purpose is not only sharing but adding data protection.

Performance

Performance

Internal storage is just one element of a computer system whether PC, laptop or server. In many cases the internal storage provided or that can be specified is adequate to match the other components such as CPU or GPU. In cases where the storage is required to provide specific high performance, the internal storage may be largely ignored in favour of specialised dedicated shared storage.

Backup

Backup

Critical data should always be backed up and external storage is a way to achieve this. However due to the dedicated nature of backup storage the security of the backed-up data can also be enhanced by using multiple drives to increase integrity. External backup storage can then be replicated in a second location if required to add additional protection.

Archive

Archive

Additional storage can be added easily by connecting an external enclosure with one or more additional drives in it. The enclosure may be temporarily or permanently connected to the computer, and used for adding to the internal storage or for protecting sensitive files if the external storage has multiple drives.

Internal vs External Storage

Although we talk about these two types of storage as opposing approaches they are truly complimentary. There will always be a need for both even if one is heavily favoured over the other - below are a few example scenarios to illustrate how they function together but not always equally.

For the Home

For the Home

A family may use multiple PCs, laptops and smartphones - all with their own internal storage. However, there may be a need to bring together photos and videos from each family member into one place where they can be safeguarded and shared whether at home or away. An external storage device connected to the network router allows exactly this, plus it creates a backup should a smartphone or laptop be lost or stolen.

For the Home Office

For the Home Office

Self-employed workers may take their laptop with them to client sites, so portability is key but a light laptop will contain limited storage capacity. An external storage drive at home allows you to offload critical data by connecting it as and when required. This external enclosure could contain multiple drives for extra capacity, data protection or both - connect it to the router and it can be accessed while out and about too

For the Large Organisation

For the Large Organisation

The more data a business has, the more critical is it that it is protected. Typically, employees’ machines will have limited internal storage (OS only) and centralised storage is used. Dedicated storage appliances store and manage data intelligently according to access need or file type, where it is also cleansed, protected and backed-up automatically - either locally, to another site or the cloud.

For the Research Organisation

For the Research Organisation

Where high performance compute is being deployed, similarly high performance dedicated storage is needed to provide data transfer rapidly enough to match server capability. In these cases, external storage appliances are likely to be software-defined and specifically tailored for optimum performance in specific workloads.

How External Storage Works

It is fair to say that at the most basic level external storage works the same way as internal storage does - in that data is ultimately stored on either a HDD or SSD. You can learn much more about the types and sizes of HDDs and SSDs available, their characteristics, interfaces and ideal usage scenarios by reading our dedicated HDD BUYERS GUIDE, SSD BUYERS GUIDE, or if you are concerned with drives for servers or high-end storage then please read our ENTERPRISE DRIVE BUYERS GUIDE.

The below table offers a simple comparison between the two technologies, highlighting how they differ and the potential advantages / disadvantages of each.

HDD SSD Comparison
Performance Hundreds of MB/sec Thousands of MB/sec SSDs are much faster
Access Times 5-8ms 0.1ms SSDs have almost no latency
Reliability 2-5% failure rate 0.5% failure rate SSDs are much more reliable
Resilience Susceptible to vibrations No moving parts SSDs are much safer to install in external storage
Energy Use 6-15W 2-5W SSD much more energy efficient
Noise 20-40dB Silent No noise from SSD
Capacity Up to 26TB Up to 26TB Similar in maximum capacities
Cost £-££ ££ - ££££ SSDs more expensive, especially at high capacities

Although the table clearly shows that SSDs prove to be favourable in almost every comparison when compared to HDDs, however some of these parameters are not as straight-forward when it comes to external rather than internal storage. For example noise is less important if an external storage device is housed in a datacentre and the lower cost of HDDs may prove a better choice for archiving data. We’ll cover these considerations in more detail later in the next section, when we consider each type of external storage device in more depth.

Types of External Storage Devices

There are various types of external storage devices that differ from each other in their features, uses, advantages and disadvantages and relative cost. The below tabs explore each in more detail.

DAS

DAS

Direct Attached Storage (DAS) refers to external storage devices that are directly connected to a computer system - most typically a standalone PC, workstation or laptop - by means of USB-A, USB-C or Thunderbolt port. DAS devices can be permanently connected to provide additional storage (desktop drives) or temporarily connected to offload data or backup data (portable drives). It is advisable to check the type of ports your computer has and that the drive is Windows or Mac compatible too. It is also worth noting that a portable external drive will be a sealed unit, whereas for desktop versions you have the option of buying a pre-populated model with a drive already installed, or an empty external enclosure for you to add a drive into.

NAS & JBOD

NAS & JBOD

Network Attached Storage (NAS) and Just A Bunch Of Disks (JBOD) both refers to an external storage device that is connected to a network rather than directly to a computer. The main advantage of this is the ability to share access to the data, allowing multiple users to connect via the network whether in the same building as the NAS and JBOD or outside, over the Internet. There are two common form factors of NAS and JBOD - desktop and rackmount. As the name suggests desktop boxes simply sits on a desk or table top and have a cable connecting them to the network. The rackmount type is designed to fit a standard 19in wide computer rack cabinet in a server, coms room or datacentre. As you may expect the rackmount type are usually higher specification devices as they are intended for much larger organisations. You can learn more about NAS solutions by reading our NAS BUYERS GUIDE.

Software Defined Storage

Software Defined Storage

Software Defined Storage (SDS) refers to complete data management systems, offering scalability, protection, compression, cloud integration and much more. Solutions like these are built by dedicated server or storage manufacturers such as Dell, DDN and NetApp. This type of storage is often referred as tiered, as a single system can be used for data that needs to be accessed all the time (hot), data that is regularly accessed (warm) and data that is archived (cold). Additional disk shelves may contain different drive types - the fastest NVMe SSDs for hot data, SATA SSDs for warm data and HDDs for cold data. The software dynamically moving data between these layers or pools, as it is accessed to increase the efficiency of the system, whilst simultaneously performing compression and de-duplication.

AI-optimised

AI-optimised

This is a development of SDS where the software has been optimised for specialised deep learning and AI workflows. Today’s AI servers consume and analyse data at much higher rates than many traditional storage solutions can deliver, resulting in low GPU utilisation and dramatically extending training times. PEAK:AIO has developed a software platform from the ground up for AI workloads and optimised for use with NVIDIA DGX, HGX, EGX and MGX AI servers. Delivering ultra-low latency and tremendous bandwidth at a price which allows more investment to be made on GPU resource and less on legacy storage. You can learn more by viewing our PEAK:AIO STORAGE and PEAK:AIO ARCHIVE solutions.

Tape

Tape

Tape storage is an older external storage solution that differs from the rest listed here, in that it uses magnetic tapes and a tape drive to read / write data, rather than HDDs or SSDs. Although many organisations have switched to disk or cloud for backup purposes, tape technology is still widely used for backup and recovery purposes, even if intelligent NAS or SDS solutions are employed for data efficiency and protection in the first instance. This is because backing up data using HDDs and SSDs or cloud storage isn’t practical as the cost quickly spirals out of control. In addition, even the best server HDDs and SSDs only have a six year warranty. In contrast, despite its slow performance, tape remains the best format for backup as it offers much lower cost per terabyte and most tapes are rated for up to 30 years. You can learn more about tape technologies in our TAPE BACKUP BUYERS GUIDE.

Data Security

When considering an multi-drive external storage solution - whether it be DAS, NAS or SDS based, it is vital to understand about how best to protect the data on your drives. This can be achieved in a number of ways using RAID technology. RAID stands for redundant array of independent disks and it is essentially spreading the data over multiple drives to remove the chance of a single point of failure. It works by blocks of data, referred to as parity blocks, being distributed across multiple drives so that in the event of failure of any one drive the parity blocks can be used to retrieve the lost data and rebuild the array. RAID levels are categorised by number and their attributes vary with each type.

RAID 0

RAID 0

RAID 0 is the fastest RAID mode since it stripes data across all of the array’s drives and as the capacities of each drive are added together it results in the highest capacity of any RAID type. However, RAID 0 lacks a very important feature - data protection. If one drive fails, all data becomes inaccessible, so while RAID 0 configuration may be ideal for gaming where performance matters but data is not important, it is not recommended for storing critical data.

RAID 1

RAID 1

RAID 1 works across a maximum of two drives and provides data security since all data is written to both drives in the array. If a single drive fails, data remains available on the other drive, however, due to the time it takes to write data multiple times, performance is reduced. Additionally, RAID 1 reduces disk capacity by 50% since each bit of data is stored on both disks in the array. RAID 1 configurations are most commonly seen when mirroring drives that contain the operating system (OS) in enterprise servers, providing a back-up copy.

RAID 5

RAID 5

RAID 5 writes data across all drives in the array and to a parity block for each data block. If one drive fails, the data from the failed drive can be rebuilt onto a replacement drive. A minimum of three drives is required to create a RAID 5 array, and the capacity of a single drive is lost from useable storage due to the parity blocks. For example, if four 2TB drives were employed in a RAID 5 array, the useable capacity would be 3x 2TB = 6TB. Although some capacity is lost, the performance is almost as good as RAID 0, so RAID 5 is often seen as the sweet spot for many workstation and NAS uses.

RAID 6

RAID 6

RAID 6 writes data across all drives in the array, like RAID 5, but two parity blocks are used for each data block. This means that two drives can fail in the array without loss of data, as it can be rebuilt onto replacement drives. A minimum of four drives is required to create a RAID 6 array, although due to the dual parity block, two drives capacities are lost - for example if you had five 2TB drives in an array, the usable capacity would be 3x 2TB = 6TB. Typically due to this security versus capacity trade-off, RAID 6 would usually only be employed in NAS appliances and servers with critical data.

RAID 10

RAID 10

RAID 10 is referred to as a nested RAID configuration as it combines the protection of RAID 1 with the performance of RAID 0. Using four drives as an example, RAID 10 creates two RAID 1 arrays, and then combines them into a RAID 0 array. Such configurations offer exceptional data protection, allowing for two drives to fail across two RAID 1 segments. Additionally, due to the RAID 0 stripe, it provides users high performance when managing greater amounts of smaller files, so is often seen in database servers.

RAID 50

RAID 50

RAID 50 is referred to as a nested RAID configuration as it combines the parity protection of RAID 5 with the performance of RAID 0. Due to the speed of RAID 0 striping, RAID 50 improves upon RAID 5 performance, especially during writes, and also offers more protection than a single RAID level. RAID 50 is often employed in larger servers when you need improved fault tolerance, high capacity and fast write speeds. A minimum of six drives is required for a RAID 50 array, although the more drives in the array the longer it will take to initialise and rebuild data due to the large storage capacity.

RAID 60

RAID 60

RAID 60 is referred to as a nested RAID configuration as it combines the double parity protection of RAID 6 with the performance of RAID 0. Due to the speed of RAID 0 striping, RAID 60 improves upon RAID 6 performance, especially during writes, and also offers more protection than a single RAID level. RAID 60 is often employed in larger server deployments when you need exceptional fault tolerance, high capacity and fast write speeds. A minimum of eight drives is required for a RAID 60 array, although the more drives in the array the longer it will take to initialise and rebuild data due to the large storage capacity.

Systems that support RAID arrays will usually have a hot-swap capability, meaning that a failed drive can be removed from the array without powering the system down. A new drive is put in the failed drives place and the array rebuild begins - automatically. You can also configure a hot spare drive - an empty drive that sits in the array doing nothing until a drive fails, meaning that the rebuild can start without the failed drive being removed first. It is also worth mentioning that multiple RAID arrays can be configured in a single system - it may be that RAID 1 is employed to protect a pair of SSDs for the OS, whereas multiple HDDs are protected by RAID 5. Ultimately however, the RAID configurations you choose need to be controlled - in the case of desktop PCs and workstations, this is usually done at the CPU chipset or software level, as basic controller features are built in in many Intel or AMD motherboards and operating software packages such as Microsoft Windows. For more complicated systems a hardware controller may be required - these are discussed in our STORAGE CONTROLLER BUYERS GUIDE.

External Storage Connectivity

Throughout this guide we’ve touched on how external drives connect to the PC, workstation, laptop or server. There is a wide range of options including USB, Thunderbolt, Wireless, Ethernet and InfiniBand - each with their own sweet spots and use cases.

USB

USB

USB is the most popular interfaces for DAS devices - designed to be connected directly to the USB ports of a laptop, PC or workstation. Transfer speeds are up to 5Gb/s (USB 3.0), 10Gb/s (USB 3.1), 20Gb/s (USB 3.2), 40Gb/s (USB 4.0) and 80Gb/s (USB 4 2.0)

Thunderbolt

Thunderbolt

Thunderbolt is a technology based on the USB-C port but it has the ability to transfer video as well as data. It is used extensively in the Apple Mac ecosystem using the same ports to connect external storage devices, monitors, power supplies and more. It has a maximum transfer speed of 80Gb/s.

Wireless

Wireless

Although there are very few wirelessly enabled external storage devices, it may be common to access a NAS device connected to a wireless router. In this case the access speeds will be determined by the wireless standard, other wireless traffic, interference, signal strength and distance from the router.

Ethernet

Ethernet

Ethernet is by far the most common network connection for external storage used in all types of NAS and SDS systems. Basic systems may feature 1 or 10 Gb/s speeds ranging up to 40, 50, 100, 400Gb/s and 800Gb/s speeds for high end systems

InfiniBand

InfiniBand

InfiniBand is an alternative network technology to Ethernet, usually deployed for demanding applications where high bandwidth and low latency are key requirements. InfiniBand scales all the way up to 800Gb/s at the high-end.

External Storage Capacity

It may seem strange to only talk about storage capacity at the end of this guide, as it may seem one of the most obvious questions to ask - what size storage do you need? However, having covered the various types of devices and their features you’ll see there are numerous factors that will decide how the capacity you choose will be used up. Let’s look at a few scenarios that may help guide you in the decisions you should consider.

A home user may start with an idea that they need 2TB of external storage as they have added up the photo sizes they have on their various computers and smartphones. On top of this basic 2TB requirement, they should consider how long it took to accumulate that 2TB and whether their current devices take higher resolution photos than their previous ones resulting in larger file sizes going forward. If they have 2TB now, then 4TB allows for room to grow with bigger file sizes. If they want to protect their valuable memories a twin drive RAID-capable DAS or NAS may be best, so 2x 4TB is now 8TB. It will be far better value in terms of time transferring files and money spent to get the right solution first time, than realising your chosen device isn’t big enough very quickly.

A business organisation will also face the same issues, but as most rackmount storage arrays can be partially populated at purchase, expansion can be handled at demand grows. What is worth considering the type of drives you use - you could start with a 12-bay NAS and populate 4x 12TB drives, giving you 48TB space. If you configure RAID 5 you will lose one drive capacity resulting in 36TB useable space. Should a drive fail rebuilding a 12TB chunk of data will take considerable time, so it may be better to choose 8x 6TB drives to achieve your 48TB in RAID 5. Not only will a 6TB rebuild take much less time, you will also realise 42TB useable space as you only lose 6TB for parity. It is also worth pointing out that is you are using more than four HDDs in an enclosure you should always choose NAS- or enterprise-grade drives, as these are designed for 24/7 runtime and have inbuilt vibration resistance to extend the life of the drive.

Although higher-end NAS and SDS systems are designed with scalability in mind, capacity is less of a concern at the point of purchase - it does become a consideration when using one or several data management features. As we’ve mentioned RAID reduces usable capacity, whereas compression and deduplication will act to increase useable space. If you are operating tiered storage, then you may compress and deduplicate at the cold layer, only deduplicate at the warm layer, and leave the hot layer untouched for fastest access. When looking at initial capacity required or adding extra drives, the type of drive and its intended layer location will impact your calculations.

Choose your External Storage Solution

DAS NAS JBOD SDS Optimised Tape
Home Use 5 5 0 0 0 0
Business Use 1 5 3 5 5 5
Performance 2 4 3 5 5 3
Scalability 5 5 0 0 0 0
Home Use 2 4 4 5 3 5
RAID or EC Protection 0 4 0 5 5 0
Data Management Software 0 4 0 5 3 0
Cost £-££ £-££££ ££-£££ £££-£££££ ££-£££ ££-£££
Capabilities ranked, from 5 = Best to 0 = Worst

Should your chosen external storage be either NAS, SDS or AI-optimised, there are further considerations pertains to your wider infrastructure including servers, networking and UPS protection. You can learn more by reading our SERVERS BUYERS GUIDE, NETWORK CARD BUYERS GUIDE, NETWORK SWITCH BUYERS GUIDE and UPS BUYERS GUIDE.

Ready to buy?

Ready to buy?

Browse our range of external storage solutions:

PORTABLE HDD DAS PORTABLE SSD DAS DESKTOP DAS - SINGLE DRIVE DESKTOP DAS - MULTI DRIVE JBOD STORAGE NAS SOLUTIONS SDS SOLUTIONS AI OPTIMISED STORAGE TAPE STORAGE

Alternatively, if you have any further questions you’d like answering about external storage solutions, don’t hesitate to call one of our friendly advisors on 01204 474747 or contact [email protected].