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By "safer" I mean that is less likely to produce file write errors, so there's no need to check file integrity after transfer.

The problem is that some buses are more optimized for speed rather than error checking.

In my experience, the safer ways are (in order):

  1. connect both HDDs internally via SATA/PATA
  2. connect 1 HDD via USB
  3. via wired LAN
  4. via WLAN
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None of those ways you list would do more error checking then any of the others. – Ramhound May 29 '12 at 16:10
Is this an actual issue you are facing? If so, what have you tried? What OS are you using? – CharlieRB May 29 '12 at 17:17
I've tried all the methods listed here in various situations. In my experience the only safe way is the first one (connect both HDDs internally via SATA/PATA). Other methods can produce undetected transfer errors, and so you are forced to do application-level error checking. (The OS i'm using is Windows) – eadmaster May 29 '12 at 17:21

If the hard drive that you are copying the data to is empty, then one possible method would be to set up the drives in a RAID configuration, so that the content from the one is duplicated onto the other. Using the RAID configuration should also ensure that the data is copied exactly and also that it has been automatically verified.

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Internal SATA3 or external USB 3.0 are going to have a negligible real-world speed difference and are generally both perfectly safe for transferring files.

In technicality, based on the principle that:
The more components there are, the greater chance of something going wrong,
then safety is as follows:


  • Internal SATA
  • External USB
  • Wired LAN
  • Wireless LAN

Least safe


  • Internal SATA has only the internal PC components to go wrong.
  • External USB has that plus the USB sub board plus the USB cable.
  • Wired LAN has the internal PC components plus the length of ethernet cabling, plus the router, plus anything behind the router between the host PC and the router.
  • Wireless LAN has the internal PC components plus interference (look it up), which is considerably more volatile than cabled transfer (relatively), plus the router, plus anything behind the router between the host PC and the router.

In general, however, you're pretty safe with any of the methods, although I would avoid wireless to transfer sensitive data for both the reasons of volatility due to interference, as well as security (interception of data transmission by a malicious nearby third-party), especially in corporate or public settings (but also in home neighborhoods).

On the other hand, if the data is highly sensitive, you should ALWAYS verify the data when transferring. There is always a risk, however small, and due to lack of human omnipotence - and lack of absolute scientific certainty due to various anomalies such as the principle of quantum mechanics which states that a single atom cannot exist at the exact same place at the exact same time (the reason human teleportation is not possible - at least not with current technology), it is impossible to predict with absolute certainty whether there was a data error or not.

In summary:

  • If the data is highly sensitive, you should ALWAYS verify the data.
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By "less likely to produce file write errors" I'm understanding that to mean "least likely to get interrupted."

A wired connection is preferable to any wireless for this.

SATA is better than USB for this, but only really if you're concerned about the USB cable getting tripped over or your USB ports/motherboard is known to be flaky.

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If you want something safe the thing to do is copy it any way you want and then verify it. On unix you could dd into md5 for both the original and the copy - if those md5s are the same it is extremely likely the data is identical. If you are really crazy about this you could also then dd into sha1 for both drives and compare that output as well.

If you are just moving files (ie don't care about the boot-ability of the drive) you're fine if you just rsync one onto the other.

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