Hi, I wanted to order my iMac with a 3TB Fusion Drive in the beginning and talked to a friend yesterday, who told me that Fusion Drive isn't that nice, because all the input output (I/O) action, that happens on the SSD will destroy it sooner or later. And because the Index is written to the SSD, then everything else, that is saved on the HDD will be destroyed too. So I'm thinking about getting only a 1TB Fusion Drive and an additional 2TB external drive, because mainly I just want to store some photos, movies, tv shows and stuff like that on it. But I would like to know what you think about this, because I would definitely prefer a larger internal disk than an additional external disk, which will need space, an usb slot and a power supply...
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Fusion Drive meant to get broken someday?
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Your friend is officially clueless. Yes, SSD drives wear out eventually. But the rest of your computer is quite likely to wear out earlier. Obviously you should have a backup. Using a computer with anything on your hard drives that you value and not having a backup is somewhere between clueless and criminal.
If anything goes wrong with the SSD drive, you get it fixed (which will mean replacing the SSD drive), and then you restore from your backup.
Ok, he sayed the fact, that the constantly moving around between SSD and HDD will accelerate this process extremely, so he thinks, the first fusion drives will be broken in about 3 years... If that's wrong and it (the SSD) will last for example easily 10 years although it's like a caching drive and has much too do all the time, I will of course get the 3TB =) I backup all my stuff either way! 
Agreed. There is no reason really to worry. It's true that the fusion drive hasn't been out very long for the Mac and yes things do fail, but i don't see the fusion drive failing any more or less than a HDD or SSD would. Over the years yes they will fail BUT your more likely to have upgraded by then. i Have ordered a 3TB fusion drive and are looking forward to the fast speeds
Plus Apple tend to use good quality parts (hence the premium prices)
It also depends what kind of SSD it is, if it's a SLC it will not break down before the iMac breaks, but if it's an MLC or even (a lot)worse a TLC I can see the first breaking after 2-3 years for a TLC, and 5-6 years for a MLC SSD.
Ok, he sayed the fact, that the constantly moving around between SSD and HDD will accelerate this process extremely, so he thinks, the first fusion drives will be broken in about 3 years... If that's wrong and it (the SSD) will last for example easily 10 years although it's like a caching drive and has much too do all the time, I will of course get the 3TB =) I backup all my stuff either way!
It's not "constantly moving around". Once everything is in the right place, it stays where it is.
And the first fusion drives will be broken much earlier than in 3 years - if Apple sells a few hundred thousand of those then some break. Purely statistics. That's why you have a backup. And some will last a lot longer. The rest is pure speculation on your friend's side.
I'm not sure this is true anymore, depending on the wear leveling algorithms. For earlier drives maybe, but I think more recent drives have good enough controllers that should extend the life well beyond these numbers. I believe the new Samsung TLC drives are supposed to live at least 10 years writing 100GB/day or something similar. Of course, the actual life is very dependent on the usage of the drive itself.
"So I'm thinking about getting only a 1TB Fusion Drive and an additional 2TB external drive, because mainly I just want to store some photos, movies, tv shows and stuff like that on it."
Post #2 claimed that your friend was "clueless", but I think he's wise.
Old saying: don't keep all your eggs in one basket. Still true.
Because the fusion drive is literally -two- hard drives "mind melded" (apologies to Mr. Spock) into a single logical volume, if one of those drives fails at some point in the future, you stand to lose everything that's on BOTH of them (SSD and HDD). I don't know of any utility out there that (in the case of the failure of one drive in a fusion setup) can "split" the fusion and make the other drive recoverable.
However, if you maintain a -third- (external) drive, perhaps with at least two partitions (one relatively small, holding a copy of your OS and apps), and the the other larger (for an archive of movies, music, etc.), you are insulated against the failure of the fusion drives inside.
The other way to do it would be to get the 3tb fusion in the iMac, but also maintain a large backup drive externally. You always want at least two copies of your important data, anyway. If you go this route, I'd suggest using CarbonCopyCloner instead of Time Machine so that your external backup is instantly bootable.
Post #2 claimed that your friend was "clueless", but I think he's wise.
Old saying: don't keep all your eggs in one basket. Still true.
Because the fusion drive is literally -two- hard drives "mind melded" (apologies to Mr. Spock) into a single logical volume, if one of those drives fails at some point in the future, you stand to lose everything that's on BOTH of them (SSD and HDD). I don't know of any utility out there that (in the case of the failure of one drive in a fusion setup) can "split" the fusion and make the other drive recoverable.
However, if you maintain a -third- (external) drive, perhaps with at least two partitions (one relatively small, holding a copy of your OS and apps), and the the other larger (for an archive of movies, music, etc.), you are insulated against the failure of the fusion drives inside.
The other way to do it would be to get the 3tb fusion in the iMac, but also maintain a large backup drive externally. You always want at least two copies of your important data, anyway. If you go this route, I'd suggest using CarbonCopyCloner instead of Time Machine so that your external backup is instantly bootable.
Yeah, well, TLC blows. Thanks for the link. It does raise an important point though; the higher capacity drives have more NAND chips and therefore longer life.
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I don't think the wear from the Fusion Drive is significant based on what it actually does on a software level, and one should always maintain a backup anyway. So while the chances of data failure are higher since either drive failure will result in catastrophic data loss, the recovery should be the same and relatively pain free either way.
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Apple currently uses Samsung SSDs in all of its computers for 256GB and up, only substituting some Toshiba (Sandforce) models for 128GB in the blade form factor. The only computers still using the 2.5" are the Mac Mini and Pros, the rest have transitioned to the blade style SSD. The 2.5"s I've heard are just OEM versions of the Samsung 830, which is highly regarded and in my opinion, vastly superior to the 840.
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As a caveat, if you plan to use Boot Camp, it is currently not supported with the 3TB HD in combination with an SSD for FD.
Yep.. the teardowns have found what appears to be an Apple OEM version of the Samsung 830, which uses MLC NAND.
The iMac Fusion drives use a 128GB SSD. So using the info Justperry linked in post #10, that drive will last at least 10 years with 10GB of writes a day (which is a lot).
I suppose theoretically Fusion might result in slightly more writes to the SSD, but from what I have read about how Fusion works, I don't see how it would be enough of an increase in writes to make a noticeable difference in NAND cell lifetime.