I have owned 4 external harddrives(3 iomega, 1 WD MyBook).

2 of them are dead and are nothing but bricks now (1 Iomega and 1 WD MyBook). Is it just me or the external harddrives very unstable ?

All the externals are basically, Internal harddrives with interface boards to USBs. whats makes them so unstable?

More often than not, the drives are fine and the enclosure is the problem. If the drives are bad, then you might consider that they are over-heating due to being left on for extended periods. I've had several enclosures die, but never the drive.

Anyway, take the drives out of the enclosures and try them internally. I like the enclosures from OKGear, (also available as MadDog) because they are solid aluminum and cool well.

IMO, the question is not easy to answer.

For example I have 3 external HDDs and all of them works perfect. One of this HDDs is a WD MyBook 500GB and I do not have any problems with it.

I could assume the problem with external HDDs is that they are not always handled as a HDD should be handled.

If I compare the lifetime of a HDD build in a desktop PC and a HDD in a Notebook the desktop HDD liefetime will be longer since a desktop will not moved so often.

I guess most of the damaged HDDs in external enclosures are related to "handling failures" (i.e. enclosure moved during HDD spin, ...)

For this reason an external HDD should be handled very carefully. Maybe this is the reason I do not have any problems, or I'm only a lucky guy...

Thanks CDan, TM for your input....here's the latest...

I opened my IOmega external harddrives..
IOmega drive(enclosure is solid aluminium) had a Hitachi IDE harddrive...I tested the enclosure with another IDE harddrive...looks the the enclosure is working fine.
And on the board below the Hitachi harddrive I could see one of the Chip is burnt, I will upload a digital pic as soon as I can get hold of a digital camera. Anyone knows if I can find a replacemen board?

will have to open my WD MyBook and see if I can find the problem.

The replacement board must be excact the same, same hardware stepping, same FW version, .... Since the modern HDDs have electronics in the aluminium casing were the read / write heads and platters are located and the interface electronic board (on the underside of the HDD). Both electronics must work with each other, for this reason it is important that the interface board ir exactly the same. A wrong board could result damaging the electronic in the aluminium casing and could also damage the replacement interface board.

The only way to get the data is asking a professional data recovery service or use the backup made on i.e. DVDs

Given the current prices for HDDs, repairing one is hardly worth the effort. I just keep a few enclosures around and fill them with whatever HDD is at hand or on sale.

I think external drives are more susceptible than internal drives to damage from handling as pointed out by TM, and some enclosures might not provide sufficient cooling.

@parvathreddy: Welcome to CDFreaks!

It might not be worth the effort to save the drive (and I personally wouldn't spend the time to do it), but saving the data on the drive is another matter and could be worth far more than the price of a new drive.

I have to agree with those reporting previously. I have about 8 computers most with two internal HD's each. In addition I have at least 12 external HD's (USB and firewire) ranging from 100 GB to 1Terabyte. Some I put into external cases and some I purchased as external drives. I never purchase an external case unless it has a fan. So far only one drive has ever failed (a 80 GB external portable which was replaced one day prior to the warranty ending and the replacement is still running about 3 years later). I have had two internal drives fail in the past 20 years.

Key factors include excessive heat, running the drive when it is not needed, rough handling, lack of adequate power protection (I use all mine on battery back-up units), brand of drive, and bad or low power USB ports. All my drives are connected via powered USB hubs (8 HD's and DVD burners to one computer) to insure adequate power even though the drive does supply power. I also have them connected in a chain through three USB hubs so they can be further away from my desk. People often forget to CLEAN their external drives - I blow compressed air through the fans to be sure there is proper air movement and open the enclosures when I can to blow out any accumulated dust. Also check the fans since they are small and can fail with no warning. I have never had a bad enclosure although a couple I have (with DVD burners installed) will not allow the firmware to be updated within the case.

The brands I have are Maxtor, Simpletech, Edge, and Fantom. The drives I put in cases are mostly Segate. The external cases are a variety of makes. I also have several older notebook drives in aluminum external cases (mostly 120 GIG) that operate with no problems.

I have (and recommend) a USB to IDE adapter that functions similar to an external case but there is no case. I use this to store files on a variety of internal type hard drives (much like flipping floppy disks or DVD's) that I pile up on a shelf over my desk. Great cost reduction when drives are not needed all that often - just be sure to have good air flow and not use the drive too long. Also great for testing and preparing other internal drives.

All my hard drive image backups are contained on one 500 and one 200 GIG external Maxtor drives (need to get another terabyte drive for this soon.) I found DVD's were to unreliable and too slow for this purpose!

So, I have been using external devices for many years (hard drive, DVD burners, CD burners) and find them to be very reliable if the proper care is taken. My portable ones travel to and from work every day in my briefcase - no problems. A couple of the external drives are connected all the time due to the purpose I use them for.

My philosophy is to have only a 200 gig or smaller internal drive in the computer and use larger external drives for the necessary storage. Having everything on an internal huge hard drive is just asking for trouble unless you do backups on a very regular basis! External drives are not running as often and thus it seems may last longer. On critical drives (external and internal) I run Spinrite on a yearly basis (or less) to check for surface defects and to refresh the magnetic tracks that store the data. The full surface scan can take hours but is worth it - use one older notebook computer just to do that.

Hope this helps. All hard drives will fail - it is not a matter of IF but of WHEN. Having backups is the best protection along with simple care. I have found that most times a hard drive failure is caused by rough user handling but they all must fail in time.

I forgot one possible reason for external HDD instability.

The external enclosures you buy seperately (and put your HDD into the enclosure by your own) are in most cases very cheap stuff. The power supplys shipped with this enclosures are also cheapest stuff. I guess the accuracy of the power is only average, maybe below average.

In a PC the power supply unit is mostly not a cheap part. When I read here in this forum most people buy good PSUs. Also Dell and other PC builder does not use cheap stuff in their PCs...

But the power thing is only a guess...

Good Point! I agree But I also tend to think that the fluctuating power in homes can further worsen this problem. I can not count the number of times my battery back-up units beep indicating a drop in power that the battery then supplies (like when the air conditioner comes on, etc.).

most of the external drives that i've had have had no problems, but it definitely sucks when they're unstable.

Enclosures without a fan will cause the drive to overheat. The latest drives don't generate as much heat as the original 7200 RPM drives and might last longer, but the older ones will toast themselves for sure.

I use the AMS enclosures I get from NewEgg. There might be better ones, and there are certainly cheaper ones, but these work for me.

If you have available SATA ports on your computer, I think a SATA drive and enclosure is much better because there is no bridge chip. No conversion from IDE to USB or firewire. Just SATA all the way.

By the way, don't think buying a pre-assembled external drive made by one of the hard drive manufacturers will guarantee success. My first external was a Maxtor and it overheated and corrupted all the data. It had no fan. Fortunately after it cooled down, I was able to reformat. Then I cut a hole in the top of the case and installed a 40 mm fan. Noisy as hell, but it still works. Someday I might slow down the fan.

But that's the first and last external drive I will ever buy. Just buy a good drive and a good enclosure and assemble it your self.

I think 3.5" drives are more prone to problems than 2.5". Where I work I get lots of broken 3.5" drives inside cases, but none 2.5" drives. 1.8" and 2.5" drives are much more resilient than 3.5". The main problem of those drives is their limited size compared to the 3.5" ones.

I suppose the 2.5 drives are designed for laptops. They consume less power and I believe they spin at a slower speed and generate less heat. They would also be subject to more mechanical shock so they may be designed to handle it.

3.5" drives inside cases will run warmer that ideal unless the case layout and fans are designed to cool them. I now have mine behind an intake fan that keeps the drive temperature below 100 F (38 C) most of the time. This is probably a bit cooler than necessary.

In the past I've had them run at 120 F (48 C) and even 130 F (54 C), but they died after a few years. It seems the warmer they run, the quicker they die.

Google published a paper with their experiences from having a gazillion hard drives in their server farms, and one of their surprising findings was, that differences in temperature didn't seem to play a role in determining failure rate on their drives.

Even though they probably use only or mostly 3.5" drives, it's reasonable to assume that the same could be true for 2.5" drives.

So who you gonna believe Drage, me or Google?

This apparently is true for drives less than 3 years old. In a discussion of Google's experience I found this: "Only in the 3-year-old disk population was there correlation between high temperatures and failure rates." That quote can be found on this page: http://lwn.net/Articles/237924/
I want my drives to last forever.

The temperature range that didn't affect failure rate (for young drives) was 17C to 55C. After using my old fanless Maxtor One Touch external drive for an hour, it got hot enough to fry eggs. It didn't destroy the drive but it corrupted the file system and made the drive unreadable.

I want my drives to last forever.
We would all love to have this but the fact is that for every current hard drive failure is a matter of WHEN and not IF. They will all fail as long as they have moving parts. Possibly when we have much larger capacity solid state hard drives they will last longer - but again nothing other than the usual death and taxes goes on forever. I still have the first 20 MEG (yes MEG) hard drive from many many years ago. Huge at the time but still running!! Others have failed in a week, year, etc. A very reliable multi-faceted back-up plan is the only way to insure your data is safe.

i have also had numerous externals go, maybe laptop cant power them well enough

anyway now i have my primary internal, its a
segate 160gb 7200 8mb buffer
and a 2ndary
wd 320 gb 5400 rpm

its in the cd drive slot since i use an external burner, i find it much more useful to have 440 gb of laptop space and no cd drive than 140gb and a cd drive

allows me to take loads of films anywhere!

After reading all the posts, & As AM is right, it's actually our carelessness, that makes external hard drives fail, but I think this is too a major extent solution for it.

Here Comes:- Wifi External Hard Disk that works with wifi lan adapters yipiee. but taking the factor of its price, a i think it's too far for Indian Customers, but do give it a try Here

Now I have to Say Apple Rocks

I wouldn't trust an external drive ever. If was given one i would remove the drive and mount it in the pc. Then throw away the external enclosure in the bin. Amount of times these enclosure electronics go bad. Always it's the hard drive and user that is the end loser. It depends on how much you value your data that you put on it. Or how often you back that external drive, to a non external drive.

Sure it's not all about bad enclosure circuits, there is poor air ventilation and cooling. Whilst many are used verticaly, easy to fall over and click click squeak click click.