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I have a 300 gig Maxtor One Touch II external USB II harddrive from about 2005 which has recently failed, and I have successfully put an older, smaller disk in there to make sure that it is the disk itself rather than the controller which has failed.

Rather than buy a completely new external drive, I am inclined to buy a bare disk and put it back in the enclosure.

My problem is, these days it's quite hard to find a 300 gig disk where I live - I'm much more likely to be able to find a terabyte and up - budget wise that's not a problem, but I don't know whether the enclosure's controller is up to the job.

Is there a limit on the size that a controller for a particular interface can handle? Is there a way to find out what it is?

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@Ramhound that's what I'm trying to find out: what is the supported size? – Rich Jun 7 '13 at 14:05

There are limits in terms of harddrives and controllers:


The first one appears at around 128GiB, so you should be safe as you had a 300GB Drive in there. The second one occurs at around 2.2TB, get a smaller disk and you should be safe.

Getting a 1TB Drive should be okay.

PS: I think you'll know about drive sizes (2.5", 3.5") and about the different interfaces...

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Looking at all the sizes offered for Maxtor One Touch II the author would actually be limited to 500.0GB and below. The interface controller in this device is the reason for this limit. I make this educated conclusion based on this specification:… – Ramhound Jun 7 '13 at 14:43

what is the supported size?

"Size" is an ambiguous term.
Do you mean the drive capacity or the form factor (i.e. 3.5" or 2.5")?

I don't know whether the enclosure's controller is up to the job.

The enclosure does not have a disk controller. The disk controller is embedded on the HDD. This has been true since the introduction of IDE hard drives.

The enclosure probably has a USB to PATA adapter.
HDD capacity is rather irrelevant to most USB-to-HDD adapters.
(The largest capacity PATA drive you can probably find/buy will be 500GB.)

The form factor, the drive interface (e.g. PATA, SATA I or SATA II or SATA 6Gbs) and power requirements (that the enclosure can provide) are the primary considerations in selecting a replacement HDD for any disk enclosure.

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Sorry, yes, I was referring to the size in bytes rather than the physical size in inches. – Rich Jun 9 '13 at 7:10

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