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Second copy

The drive that holds the copy you would actually miss

The second copy of files nobody could recreate is the cheapest insurance on this site. Size the drive at about twice the files you cannot replace, connect it over USB 3.0 or faster, and keep it unplugged between copies.

By

Start from what you cannot replace

A routine that tries to copy everything runs slowly, fills its drive and gets switched off. List what cannot be replaced: photos and video of people, documents you wrote, tax and medical records, anything made rather than downloaded. Size the drive at about twice that, so older versions and a few years of growth fit.

A second tier, costly but replaceable, like a ripped movie collection or projects you could rebuild, is worth copying with less ceremony. Anything you can download again belongs in neither.

The feature nobody quotes: can it be unplugged?

Anything permanently connected can be reached by anything that reaches the computer, including ransomware running with your own permissions. A drive that is plugged in, copied to and unplugged again is unfashionable and effective. Monthly is enough for files that change slowly.

The usual rule is 3-2-1: three copies of what matters, on two kinds of storage, one of them at another address. Two drives rotated between home and a relative’s house or an office cover theft, fire and water, which no second drive on the same desk can.

Read the port, then the speed

A hard drive sustains roughly 150 to 250 MB/s; the published figures on this page are 190 MB/s for the BarraCuda and 250 MB/s for the WD_Black D10. USB 3.0 (5 Gbps) carries that comfortably, so 1 TB copies in about an hour and a half. On a USB 2.0 port, at a real 35 MB/s or so, the same terabyte takes about eight hours, and only the first full copy is that long.

Check the power, too. A 3.5-inch desktop drive needs a wall outlet; a 2.5-inch portable runs from the USB port. Neither desktop listing below says how it is powered, so look at what is in the box.

Versions, not a mirror

A copy that mirrors a folder exactly also mirrors a mistake. If a file was overwritten on Tuesday and the copy ran on Tuesday night, both are now wrong. In Time Machine, File History or whatever software you use, check how many versions are kept and how far back they go. Those versions only exist while the drive has room, which is why the capacity rule above doubles the total.

Automate it, and get told when it stops

Schedule the copy, and turn on whatever alert the software offers when a run fails. A routine that silently stopped four months ago is worse than none, because you have been relying on it. Put a quarterly reminder in a calendar and restore one folder while you are there.

Drives on this site

Prices read on Amazon.com on October 25, 2026:

More on our external hard drives and internal hard drives shelves.

What a backup drive cannot do

It cannot help if it has never been tested. A copy nobody has restored from is a copy nobody knows works, and the moment you find out is always the worst one.

Which situation is yours?

The copy has to leave the home
Format and ruggedness count for more than speed.
The drive stays plugged in
Stated power decides: bus-powered or with a mains brick.
The volume is large
The mechanical drive takes the advantage back over solid state.
Copying is frequent
The stated interface becomes the limiting factor.

Picking by what you run

The Sunday copy

A drive plugged in once a week, then put away in a drawer somewhere else.

The cold archive

A drive almost never plugged back in, and therefore one to check now and then.

The working buffer

Here the stated interface and the memory type change daily life.

The specifications that decide

The stated capacity
It is compared against the volume to back up plus margin, not against today’s volume.
The stated power
Bus-powered or with a brick: that decides what you carry and where you can plug in.
The published interface
It caps the copying time. Over hundreds of gigabytes that is measured in hours.

Which figure for which household

The useThe criterionThe false criterion
Weekly copyThe capacitySpeed
Archive stored elsewhereRuggednessThe interface
Frequent copyingThe interfacePrice per terabyte
CarryingThe powerThe styling

The usual wrong turns

Leaving the copy next to the original
A backup drive sitting on the machine protects against neither theft nor a burst pipe.
Never checking the copy
A backup never read back is a hypothesis, not a backup.
Choosing capacity to the exact figure
The volume to back up grows. Margin avoids buying again in a year.

By the household and its devices

The careful household
Two drives that alternate, one plugged in, the other elsewhere.
The photographer
Capacity first, and a regular check that the files still read.
The traveler
Looks at stated power and ruggedness before anything else.

Firmware, heat and working life

An external drive spends its time put away, then takes a journey, then works for hours. It is knocks while parked and the connector that kill it, more than wear.

  • Eject properly before pulling the cable.
  • Carry the drive in a case, never loose in a bag.
  • Plug cold archives back in now and then to check they still read.
  • Replace a cable whose connector has play: it is the commonest failure.

Safety

This site publishes stated specifications and describes no backup strategy.

  • Stated encryption protects a lost or stolen drive.
  • A single copy is not a backup.
  • A drive dropped while running gets replaced, not tested.
  • Bundled backup software comes under its own publisher.

Prices quoted in this text were read on October 26, 2026. The live price is at the top of the page.

What we shortlist, and why

  1. External hard drives

    Intenso 1 TB Portable Drive, Refurbished

    1 TB · 2.5-inch portable · refurbished drive in a new enclosure, tested in Vechta, Germany · USB 3.2 Gen 1 (5 Gbps) · 85 MB/s read, 75 MB/s write · 5 × 3 × 0.5 in

    A refurbished 1 TB portable drive, tested by Intenso in Germany and fitted in a new enclosure, rated 85 MB/s read and 75 MB/s write over USB 3.2 Gen 1, at $82.58. That is about $83 per terabyte.

    Best for: A small, bus-powered drive for a second copy of documents and photos that fit in 1 TB.

    7.4/10

    ≈ $83

    Check price on Amazon Read the review: Intenso 1 TB Portable Drive, Refurbished
  2. External hard drives

    Avolusion PRO-T5, 4 TB, 2-year warranty

    4 TB · format not published, 178 × 127 × 25 mm (7.01 × 5 × 0.98 in) and 1,361 g (48 oz) suggest desktop · USB 3.0 · connector not published · power source not published · no rate published · 1,361 g (48 oz) · no cable published · two-year warranty

    Four terabytes and a two-year warranty for $158.50 on Amazon.com on October 26, 2026, on a listing whose four bullets publish no figure beyond the capacity.

    Best for: Four terabytes with a warranty on a desk, where the details can be checked on the carton.

    ≈ $159

    Check price on Amazon Read the review: Avolusion PRO-T5, 4 TB, 2-year warranty
  3. External hard drives

    Seagate 6 TB desktop, dimensions in the title

    6 TB · titled desktop, described as portable in the second bullet · USB 3.0 · connector not published · power source not published · no rate published · 178 × 41 × 124 mm (7.01 × 1.61 × 4.88 in), published in the title · 1,176 g (41.5 oz) · no cable, no warranty

    Six terabytes with its dimensions in the title and its power supply in the box — and a listing that calls itself a desktop drive and then calls itself portable.

    Best for: Six terabytes that will sit on a desk and stay there

    ≈ $229

    Check price on Amazon Read the review: Seagate 6 TB desktop, dimensions in the title
  4. External hard drives

    WD_BLACK D10 Game Drive, 8 TB, 250 MB/s, active cooling

    8 TB · titled portable, specified as a desktop unit · USB generation not published · connector not published · two 7.5 W USB Type-A charging ports · 250 MB/s stated at 7200 rpm · active cooling · 195 × 125 × 44 mm (7.68 × 4.92 × 1.73 in) · 980 g · warranty not published

    The largest capacity on this shelf and the only drive here with a fan, a spindle speed and a pair of charging ports — at $397.04 on Amazon.com on October 26, 2026.

    Best for: A console beside a television, with a controller charging off it

    ≈ $397

    Check price on Amazon Read the review: WD_BLACK D10 Game Drive, 8 TB, 250 MB/s, active cooling
  5. Internal hard drives

    Seagate BarraCuda 8 TB, 190 MB/s sustained, no rpm published

    8 TB · 3.5-inch · height not published, 26 mm (1.02 in) recorded · SATA 6 Gb/s · rotational speed not published · cache not published · 190 MB/s sustained at the outer diameter · no workload rating · no warranty · no MTBF · no acoustic figure · no idle power · 630 g (22.2 oz)

    The cheapest terabyte on this shelf at $35.00 on Amazon.com on October 26, 2026, and the only listing here that states its packaging — with a 190 MB/s sustained rate and no rotational speed.

    Best for: Bulk storage filled once, where sustained read speed is the figure that matters

    ≈ $280

    Check price on Amazon Read the review: Seagate BarraCuda 8 TB, 190 MB/s sustained, no rpm published

The questions that come up before an order

How big does a backup drive need to be?

About twice the files you could not replace: photos, videos of people, documents you wrote. The extra half holds the older versions that recover a file somebody saved over, and the growth of the next few years. Anything you can download again does not need to be on it.

Is one backup drive enough?

It is far better than none. Two drives rotated between two places are better still: a drive left plugged in beside the computer shares its building, its power strip and anything that infects it.

External drive or a second drive inside the desktop?

An internal drive is quiet, cheaper per terabyte and always available, but it shares the machine. An external drive can be unplugged, which is what protects it from ransomware. Many households do both, and an internal 3.5-inch drive in a USB dock becomes an external one.

Do I need to check the copies?

Yes, and it takes minutes. Restore one folder from each copy and open the files. You are testing that the copy is readable, that you remember how to reach it, and that it holds what you think it holds.

Each pick, and who it suits

Intenso 6021660 · $83

For homes that: A small, bus-powered drive for a second copy of documents and photos that fit in 1 TB.

Main advantage: Says plainly that it is refurbished, and where and how it was tested

Main shortcoming: About $83 per terabyte, against about $38 for the Seagate Expansion 6 TB on this shelf

Read the full review: Intenso 6021660 →

Avolusion T5-WH-4TB-XF · $159

For homes that: Four terabytes with a warranty on a desk, where the details can be checked on the carton.

Main advantage: A two-year warranty in the title, where the Intenso, the Seagate and the WD_BLACK publish no term

Main shortcoming: Four bullets and one number: no format, rate, connector, power source or cable

Read the full review: Avolusion T5-WH-4TB-XF →

Seagate STKP6000400 · $229

For homes that: Six terabytes that will sit on a desk and stay there

Main advantage: The lowest price per terabyte on this shelf, $38.17, at $229.00 on Amazon.com on October 26, 2026

Main shortcoming: The second bullet calls a 6 TB desktop drive weighing 1,176 g (41.5 oz) portable

Read the full review: Seagate STKP6000400 →

Seagate ST8000DM004 · $280

For homes that: Bulk storage filled once, where sustained read speed is the figure that matters

Main advantage: Publishes a sustained transfer rate, 190 MB/s at the outer diameter, which describes what the mechanism delivers

Main shortcoming: No rotational speed and no cache size, which every other drive here prints

Read the full review: Seagate ST8000DM004 →

What each band of spending connects

Entry level

$83 – $131

4 models

Mid range

$159 – $226

5 models

Upper range

$229 – $400

4 models

What marks the bands out: Capacity — Entry level 2 · Mid range 4 · Upper range 8

One line, then the detail

Pairings that help here

Box against box, where the comparison is already on the site.

What this page is built from

The hardware listed is taken from the catalog of this site. Specifications are the ones the manufacturer states and the ones on the Amazon page; prices are the Keepa reading for the date shown, and both change. Ranking follows declared specifications, stated strengths against stated limits, and price. Nothing here has been racked or benchmarked by us, and no page claims it has.

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