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Will the wrong hard disk controller corrupt data if I only try to read it?

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by jacko99 3 views

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Regarding swapping hard disk controllers to recover data from a non-functioning hard disk, will the wrong controller corrupt the data on the hard disk if I only try to read this data (and not write new data to this drive)? I realize that I should try to match the controller exactly, but if it is not available, as on eBay, do I risk data loss with a near match of controllers--for example, a controller from the same manufacturer and series of hard drives, but of a different size than the drive which is not functioning (e.g., 240 MB, not 340 MB)? Elsewhere, there are discussion threads noting that even two supposedly identical controllers can differ and that sometimes a manufacturer may use the same controller for more than one model: I am not trying to argue the unknown, but rather trying to find out if just trying to read the data is dangerous. That is, is it OK to look, but not touch, or do I get to the point of touching willy-nilly?

6 replies

by oh smeg

But I certainly wouldn't recommend using anything but the exact same Model Number and Revision Number Circuit Board on any HDD.

Even during a production Run different HDD of the same Model & Size may have different controller Boards which doesn't hurt till you start to change things around.

Of course if the data would only be [b]Nice[/b] to recover you're not going to be much worse off by giving it a try but realistically you are likely to hose the Data on the Drive and force a Full Forensic Recovery if it simply must be recovered.

If it's [b]Important[/b] pay a Data Recovery Specialist who specializes in working with dead drives to get the data back.

Col

by jacko99

Thanks. Well-taken. Data recovery pros are useful, and in no way would I want to diminish them. However, I shouldn't have to go directly to the operating room, when Bandaids may be all that I need. I suspect that a high percentage of work, not to mention revenue, at the data recovery shops comes merely from swapping controllers--a job that almost any member of this site should able to do. I concede that the controller may not be the only issue--if so, upon learning the magnitude of the problem, I would be more inclined to hire a pro at that point. Meanwhile, if I read you correctly, I hope to learn why an inexact controller would be fatal in an attempt just to read the hard drive (but not write to it???the recovery would be to another drive). Perhaps I would get some type of message to the effect that the disk is unreadable or maybe it would read back junk, but I fail to understand why the data would be altered without a Save, Fix, or Format command.

by oh smeg

Is that the way that the Data is Mapped is controlled by that Card. When you first turn on the system it does a control Read/Write to the HDD and if you use the wrong controller card it may then proceed to remap the Drive Root Information making a Forensic Recovery mandatory.

Here it's not so much the IC's involved in starting the Platters Spinning or controlling the speed that they spin at, but the Electronics used to run the Stepping Motor which moves the Read/Write Heads across the Platters and how that Magnetic Signals are interpreted by that controller card.

A Platter set will be Mapped and written to in the form that the Electronics specify and if you change the controller card they may cause the drive to be written to in a different manner which causes the existing Data on the drive to become unreadable.

You also should be aware that if there is a fault inside the HDD which blew a Controlled Card it will blow any subsequent Controller Card that you fit to the HDD. That would render 2 HDD unusable.

I do a small amount of Data Recovery and have never changed a Controller Card on a HDD in a successful fashion. At least I've never been able to recover any data by just changing a Controller Card. Generally if something has happened to the HDD to make the fitted Controller Card stop working the fix is far more involved than just changing the card. ;)

Col

by dougcollinsuk

It is almost impossible to stop Windows checking and writing to the drive you are attempting to recover - so the safest option is to use a bootable CD tool such as Acronis to clone the damaged hard drive onto a new disk. Assuming the drive is detected and Acronis can read it - you can then examine the copy with no damage to the original.

I have replaced controllers on a few occasions and recovered valuable data. My most notable case was where I recovered a network server hard drive with total success - one of the controller chips developed a short and burned a neat hole in the chip casing while I was testing the drive.

The closer the match the more chance you have of success - but as others have said there is always a risk. Always check the drive is correctly detected in the BIOS before proceeding with any recovery opertaions. Obviously replacing the integrated drive controller will only work if the rest of the drive is in good health

Assuming the cost of professional recovery is not justified - but the data is worth recovering then other methods are worth a try.

by spitfire_sysop

You can open a drive with read only NTFS drivers in Linux and be pretty sure that it won't write anything to the drive. I imagine that if you had the wrong controller that it simply would not read at all. If the controller is for a different size drive then it could have totally different information for sectors, heads and clusters. This means it would not know where your data begins and where it ends. I am not sure how the controller would handle this because I have never done it.

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