It could be part of the motor. The 1st pic is my hdd with the small piece missing. The 2nd pic is a good hdd. Is it still usable or do I have to send a RMA? Thanks for anyone giving a reply.

These both appear to be NORMAL....

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You may be right. I bought it a long time ago and I just find the difference. But the hole in the above pic is deeper than below and something seems should have been there. I can not take a clear photo due to the poor camera. Here is another shot and the out circle colored dark yellow in left is not metal but something soft. Instead the silver area in the right is metal. I guess some metal cap or sealer used to be there but now is missing.

No
There are different kinds of bearings and both bearings on the picture are fine and do not miss any parts

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Thanks for your comment. These pics are taken from two hdds of the same model and I bought them together from some retailer some time ago. So there is quite a small chance that they use different bearings for products of same date of manufacture. I have never seen the bearing used in the left pic while all my other hdds use the right one, so I am a little confused.

Only thing confused is that you are not listening to Doomer

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You don't have to backup all of your files, just the ones you want to keep.

Seems you are the one not listening. I said the two hdds are of same model, same date and place of manufacture. Are you trying to say that they use different bearings in the same production line?

I guess you already know the answer to your question then, since you are telling everyone who is answering it they are wrong

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You don't have to backup all of your files, just the ones you want to keep.

My question is if it is still usable or need a DMA, which I still have no answer.

I may have been giving the wrong information and I apology for that. So now let me narrate my problem more clearly. I got some part on the back side of this hdd missing. Now I need to know if this hdd will work as usual and last as it's expected or it's going to fail soon and catastrophically.

You already have the answer. If your concerned, RMA them assuming there is some issues. If not, test them. If they are in working order, use them. If your still unclear, trash them.

Excellent reply. Plus if I get countless spare hdds I will just throw away this one and not bothering here. RMA is quite inconvenient here and not everyone is a mechanics or hardware expect with testing experience. I was expecting some advice from someone with knowledge about the details of a motor, not rules from the book or a customer service.

Here is an excellent advice: why don't you buy about 20 more drives of the same model from different locations in the world and then assess the drive's motor design and draw your own conclusions?!?

As far customer service: what don't you call the manufacturer and ask them the question you want the answer for and see how much knowledge they will provide to you.

Your lack of knowledge about the forum members' knowledge should not be a rule from your every day's book of rules pertaining to how to question someone's knowledge.

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Let me tell you: next time you just say "Figure it out yourself" when you are asked a question that you have no idea of since it is better and conciser than a tedious and unrelated talk.

Your conclusion is not correct
Different drives of the same model can use different bearings, in fact it is more than two kinds of the bearings. The drives on your picture look like Seagate drives. I've seen these models with 4 different bearings

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But you already HAVE the answer. Very precise and very clear.

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