2.5 vs 3.5 HDD

4 months ago by pastermil to c/datahoarder

I'm looking to get a new internal hard drive for a specific use case:

it's for a desktop, meaning I can fit either
i need 2TB, no more and no less, also meaning I can get either
it's for my media collection, mostly movies
it's not gonna be read-only, but I wouldn't write too often (I would torrent, but all the program's metadata would be on another drive)
most likely gonna be formatted with btrfs (subject to change, open to suggestion)

Should I get the 2.5 inch or the 3.5 one?

Thanks in advance.

Korkki 8 points 4 months ago

Should I get the 2.5 inch or the 3.5 one?

If you have the space and mountings in the case then 3.5 naturally. larger drive offers more bang for the buck and that's the most important part when thinking about bulk storage after, storage size and reliability. Things like reliability, noise, write and read speed are more of a question about the model and manufacturer, not the drive dimensions. IMO things like energy consumption when thinking about hard-drives in a PC build are irrelevant, but there 2.5 inch might shine.

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pastermil 2 points 4 months ago

Not sure about the bang for the buck, as the 3.5 tend to be more expensive where I'm at. Worry not, tho, I won't be a cheapskate for when it matters.

As for the size, I'm looking for exactly the 2TB one, for which there's no issue in finding either.

As for the manufacturer, I'm leaning more toward Seagate, which have both types. I already have a few from them, one of which is a 2TB 2.5 HDD for a laptop, which I'm happy with. This one will be for my desktop.

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Mohamed 4 points 4 months ago

I think there isn't much of a difference in your case, but, also, 3.5" are generally a better choice than 2.5" in all aspects except portability.

Higher performing HDDs tend to be 3.5", which might have higher RPM (higher read and write speeds), and bigger solid-state cache to speed up writes. I think 3.5's tend to be more fault-tolerant too.

In your case, you probably wont need more than the average read speed. A large write cache could be useful, especially if you have a fast internet: if your cache is too small, your download speed will be capped by the write speed of your HDD. Torrenting writes in random access rather than sequential, and random access writes are quite slow on HDDs.

You can circumvent the write cache problem in several ways:

Get an HDD with a large write cache.
Download to a faster drive first, eg. an SSD, and then move it to the HDD. (While it is true that moving from the SSD to the HDD, you would still be capped by the HDD speed, sequential write speeds are usually quite a lot faster than the random access writes that torrenting needs.)
Use a write cache drive as part of a filesystem. For this, I am most familiar with ZFS, which can have an HDD device combined with an SSD write back device to speed up writes. I think bcachefs can do this too. I dont know if btrfs can do this.

If you are torrenting to the HDD directly, then use a 4K extent size for btrfs or ZFS.

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pastermil 2 points 4 months ago

I've read that larger cache size can be an indicator of SMR drives. Other than that, I don't really care about it.

To confirm your uncertainties, I can indeed use the external caching mechanisms on btrfs.

How much would the RPM affect things? I'd think the lower RPM would be less problematic, at least where longetivity and noise is concerned.

Also, what's your reasoning for the extent size?

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Mohamed 1 point 3 months ago

Sorry, I realize now that I actually don't know this much about HDDs. I dont know about SMR, or how rpm affects longevity.

The extent size was suggested by ZFS docs: https://openzfs.github.io/...

(I made a mistake. They're recommended record size is 16k)

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Hiro8811 2 points 4 months ago

I'd say 3.5, easier to find a CMR disk which you want for a NAS especially if you seed. I suggest you buy two if you can for a backup. But keep in mind HDD optimal temperature is between 12 and 45, it took me 2x140mm fans running at 1500 rpm to keep at 40%

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ThorrJo 2 points 4 months ago

2.5" is almost certainly SMR, which you don't want.

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timewarp -2 points 4 months ago

Lol you should get a M.2 then.

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Korkki 3 points 4 months ago

If the use is media and file storage, then ssd is not a cost effective solution.