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Build an external USB hard disk

Build your own external USB hard disk

An external USB hard drive is a supremely useful device, since you can store a very large amount of data on one. A 500GB disk is commonplace now, and will hold a lot of data, disk images, backups, films, and music.

You can buy a ready-made external hard drive - or you can build your own. A standard PC hard drive can be placed externally in a USB-linked enclosure, and this provides simple and easily used backup storage. There are several advantages to the DIY route.

Venus SATA and ATA USB enclosures

Venus SATA (left) and ATA (right) USB enclosures, with cooling fan

Disk image backups

An important use is for disk images and other backups. The easiest and quickest way to save your data is to run a disk image backup, which takes about 15  or 20 minutes to grab the entire disk contents off your PC - much less for a small hard drive. Macrium and Acronis are popular programs to do this with, and are also available free. A disk image normally produces a file of around half the size of the original amount of data on the PC's hard disk, so that a file of 10GB will result from a PC drive with 20GB of data on it - regardless of the size of the actual disk, which might for example be 160GB.

Why build your own USB disk

From personal experience I can tell you that pre-built USB disks are often not a good idea. This is especially true when there is no inbuilt fan, as the disk gets very hot. This reduces its reliability and life expectancy - not a good idea when it's your vital data in there. Also, if the enclosure electronics fail - as they do - it's a nightmare trying to get the disk out to place it in another enclosure or a PC in order to recover the data. You need a hammer and chisel to open some of these proprietary enclosures.

In contrast, a DIY USB disk can be opened easily and the disk replaced in seconds. I feel this solution is better because having had a proprietary external hard disk die on me, I've found the best solution is one that (a) has a cooling fan, and (b) allows you to swap the disks fast. You can't swap out the disks easily in a pre-built assembly, you need a manual on how to open it or a large hammer. A DIY USB disk is always going to be better, even if it costs $10 or so more.

Advantages of a self-built USB disk:
You can choose the disk size, and the enclosure type
You will always choose one with a cooling fan
Inserting the new disk takes seconds
Replacing a disk takes seconds

Disadvantages of a self-build external hard disk:
It will cost about $10 or $20 more than a pre-built one

Disk terminology

A hard disk = a hard drive = HDD = a 3.5 inch disk = a standard PC hard drive.

These are all the same thing. Watch out you don't get a 2.5 inch hard disk, these small ones are used in laptops. However, you can get a smaller enclosure, specifically for 2.5" disks, and use one of these if small size is important, perhaps for travelling.

USB disk temperature

A cooling fan is vital - always buy a USB disk enclosure with an integral fan. If you don't, the whole thing gets so hot you can fry an egg on it. As the internal temperature and that of the hard disk will be 80 degrees C or so (nearly 200 F), the disk's reliability and life are bound to be affected - the normal working temperature of a hard disk is around 32C in a PC, and certainly below 50 degrees C.

I use the Venus brand enclosures, there are both ATA and SATA versions with fans. So as an example, you could get a Venus SATA USB enclosure with fan, and a Seagate 500GB disk to go in it. You'd also get the Seagate Disk Tools including the Acronis disk image program. This will give about the best modern backup system you can get.

How to tell if your disk enclosure has a fan

There is only one way to be sure - open it and see. Otherwise, perhaps you can tell by:
  • If the box surface stays cool, it's got a fan
  • If the box surface gets hot, there is no fan
  • Sometimes the faint draught of air expelled by a fan can be felt at one end

USB external disk types

You can get either an IDE-ATA (actually termed PATA) enclosure, or a SATA enclosure. Then, buy a hard disk to suit, or use a spare disk. The ATA type is for older disks, so you can use old spare hard drives in it. The SATA type is for all new disks. If you get your own box and hard disk, you can put them together for a better system than you can buy.

You need a SATA or ATA box, according to the drive you've got spare. If you're buying new, get a big SATA disk and choose a box to suit. It's complex at the moment, there is SATA, SATA2, eSATA, and maybe more to come.  This is why I prefer not to buy into any new technology or operating system for a couple of years...

The Venus enclosures are cable-less as well, you just slot the disk in. The SATA ones are really smooth, though the ATA ones need a bit of jiggery-pokery as the older power and data sockets are cruder.

I could tell you to google for the boxes, but I tried and there were a zillion results, mostly wrong, so here's a link to a UK firm that does the SATA (but not ATA) versions:

The boxes I use are:-
  • ATA: Venus USB external hard disk enclosure with fan: code JJ-23VB2
  • SATA 1 & 2: Venus USB external hard disk enclosure with fan: code JJ-23VSU

You'll have to find a national mail-order firm in your region. In the UK I used Scan (SATA versions) and Misco (ATA version). Note that these are the new box versions from Venus - actually Jou-Jye at:

Take a look at the page link I gave above, and the photos below, and look at the boxes' appearance (rounded edge shape). A lot of wholesalers (especially in the US it seems) still have the old version with a squarer shape, black, and large end-caps. I don't think you want that one. The new shape has the rounded profile, and I've listed the model numbers above.

I don't stand the disk boxes on edge, I stick 4 rubber feet on them and lay them flat. Up to you I guess, it just makes me happier to have them work 'right way up'.

Venus enclosure on edge stand

Venus enclosure mounted on its edge stand

Venus USB enclosure with rubber feet

I stick 4 rubber feet on the bottom and lay them 'right way up' - I don't use the edge-stand (on right)

You can also label the box with its type and the disk size - a good idea when you have several

Stacked Venus boxes

Stacked enclosures with rubber feet underneath - USB hub at left

USB disk connections

The disk enclosure connects to the PC with a standard USB A to B cable. You can also find enclosures with a Firewire option as well. The power connection is to mains electricity via the usual small 12volt PSU.

Venus box - back panel viewHere is the back panel view

The 12v PSU is to the left, and the cable plugs in at left

The USB cable plugs in at right, and here I've hooked it up to a 7-port stand-up USB hub at right

This USB hub is the best I've found - it has a metal case, and its own power supply

Rear panel view of ATA enclosure

ATA enclosure, rear panel view

On/off switch at left, USB socket centre, 12v power socket at right

Build a USB disk step by step

1. Decide what size of hard disk you need. Disk size is irrelevant, a 20GB or 500GB disk makes no difference, so it makes sense to get a big one. A basic SATA disk is the best choice - for example a 500GB SATA disk. It's just a standard PC 3.5 inch hard disk.

2. Order the disk. Make sure to get a 3.5 inch disk, the standard PC hard drive item. Don't get a 2.5 inch disk as these are for laptops - they work OK of course, but are smaller and slower, and they need a small disk enclosure - which is a different model.

3. Decide if you want the standard USB-connected enclosure, or Firewire as well.

4. Order the disk enclosure. I recommend the Venus make, but there are others. Get a SATA box for a SATA disk, of course. If you are using a spare old ATA disk - then get an ATA box to suit, which is often called a PATA disk box in this field. A PATA box = an IDE-ATA box = an ATA box.


6. When it arrives, check the disk and enclosure to make sure you received the correct, compatible ones, and that the enclosure has a fan.

7. With a crosshead / Philips screwdriver, open the box and slot the disk in. SATA disks connect easily, the connections are very smooth. The process only takes a few seconds. ATA disks and boxes need some jiggery-pokery as the connections are cruder and do not line up so well. I find that a plastic cable tie wedged under the box connections helps to line them up - then it can be withdrawn.

8. Close the box, hook up the USB cable (included with the box) to the PC, and the power cable to the mains via the small PSU included.

9. When the the PC is on, click the power switch on the back of the USB box. The PC will recognise the USB disk and auto-connect in a few seconds. No drivers are needed. There is a driver CD with Venus boxes but it's only needed for Windows 98 etc.

10. You can find the icon for the USB disk via My Computer. It will be called something like External Disk E:  or Removable Disk F: or USB Disk G: etc. The disk can be used like any other on the PC - just drag 'n drop files onto it or run your backups to it.

11. With some PCs you will need to switch the USB disk on one minute before the PC boots up, in order for the operating system to see the disk. This applies especially when booting to a 'pre-boot' environment such as BartPE, UBCD4Win, or Acronis loader, when reinstalling a disk image.

12. Some (but not all) of the Venus boxes have a fan speed control. I find it only needs to be on Low, but maybe if you are in the tropics and working the disk hard, you may need it on high. Just feel the surface temperature of the box - if it's warm it's fine, but if hot then turn the fan up to High. The box surface stays remarkably cool, in contrast to store-bought USB disks, which get red hot as usually they have no fan.

13. Hard disk maintenance: if you are using your USB disk as a normal PC disk, for general storage, backups and so on, then treat it as a normal PC disk. That means it needs defragging occasionally, and redundant files cleaned off it. Defragging a 500GB disk is an overnight job :)

14. Please let us know what disk boxes you found to be good or bad.

The Venus ATA USB box opened

The Venus ATA enclosure opened up - about 5 seconds work

Close-up view of open box and disk

Close-up view of the ATA enclosure and hard disk - about 10 seconds work to slot the disk in

Best storage solution for large amounts of data

A self-built external USB hard disk of around 500GB is the best way to store your disk images and large quantities of data. Because it is not difficult to change disks, you could fill a disk and change it out for a new one, keeping the full disk safely as a data backup. If the data is crucial then the disk can also be imaged to another, using Acronis for example. The disks can be vacuum-packed and stored away, using a food sealer and enclosing anti water vapour packs, available from camera suppliers. The disks should be kept away from any magnetic source such as a loudspeaker. Although this is magnetic disk technology and in theory has a finite life, I would expect the data to be secure for many years. At present, optical disc technology means data storage size is limited and costs are high; plus data life is if anything shorter (many CDs have already failed).

How to store CDs long term

Never store CDs or DVDs in jewel cases, and especially not in jewel cases with printed inserts. The discs fail for two reasons: water vapour plus oxygen corrodes the minutely thin aluminium layer the data is on. Just ordinary damp air does it. And if the disc is in a jewel case, then this process may be accelerated by a factor of 100 as the glue in the case plus chemical vapour in the printing ink can combine to form a more corrosive vapour.

To store CDs long-term you should package them in a warm, dry environment. Do not use jewel cases. Seal them with a food sealer, along with anti water vapour packs as are included with cameras.
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