johnlane
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Are there any size limits on USB hard drives?

Thu Aug 02, 2012 3:39 pm

I've been searching around for a definitive answer but so far drawn a blank. Is there a maximum size for a hard drive connected over USB? Can you go beyond the 2TiB limit, for example?

On a related subject I have been looking for a simple SATA to USB connector for this project. I hope to avoid those bulky all in one IDE and SATA things from china. I want to keep it small so it has minimal bulk for putting in a box. What I'm thinking of is nothing more than a wire with a USB plug on one end and a SATA plug on the other end. Has anyone else found a decent and simple SATA to USB adaptor?
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Lob0426
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Re: Are there any size limits on USB hard drives?

Thu Aug 02, 2012 5:57 pm

Right now I am using a 640GB seagate GoFlex drive. It is a 2.5" form factor drive. It is very compact. If you want to stay compact, you will pretty much be stuck with the laptop size drives. If you go to a 2TB drive it will need its own power supply to work. They are about the size of a large novel. The small drive like mine is powered by the USB. I also have used these?

http://www.newegg.com/Product/Product.a ... 6812816095

They work very well but have a 640GB limit. The silicone sleeve gives you short circuit protection, but you cannot get anything to stick to it for mounting. It has a "Y" adapter USB cord.
USB HDD's are not as fast as the SD cards are but are more versatile. For example, Irgun a larger swap file with more aggressive settings than the SD cards can have. And a whole lot more storage.
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Jim Manley
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Re: Are there any size limits on USB hard drives?

Fri Aug 03, 2012 4:01 am

Not sure what you're using for a USB HDD, but, many (even 5,400 rpm) can operate right at the practical upper limit (~40 Mbps sustained) of USB 2.0, and some can easily run 120+ Mbps on USB 3.0. Solid-state drives (SSDs) can go faster than either SD cards or USB flash drives, but, since the cost of the cheapest ones is twice that of a Pi and none of the above can go faster than the USB 2.0 speed limit, SSDs are a complete waste of money with the Pi. SSDs do have a vibration/G-limit advantage and otherwise can't suffer head crashes at any time (the way hard disks can). However, over time, SSDs will degrade from write fatigue, eventually to the point where their redundant internal storage is no longer able to make up for lost flash cells, if there is a swap partition on them or writes are otherwise performed continuously over long periods of time (months to a couple of years, depending on the rate).

If they had used a Compact Flash (CF) interface instead of SD, we could plug the old IBM (later Hitachi) Microdrives that were ~1-inch diameter hard drives in a double-thickness (Type II) CF package.
ImageImage
They only had capacities of 170 MBs to 12 GBs (for Seagate - only up to 8 GBs for Hitachi) though, so the smaller ones would really only be useful for swap or other high-write-rate uses. They could be hooked up to a Pi with a multi-way USB adapter that includes a CF slot (not sure all of those adpaters are Type II compatible, though). They would also need to be powered via a USB hub, as they draw upwards of 300 mA, especially when spinning up.

They're as cheap as a few dollars on auction sites, though, costing no more than their SD or CF flash memory-based counterparts, even if never used.
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jdbennet
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Re: Are there any size limits on USB hard drives?

Fri Aug 03, 2012 6:13 am

"Can you go beyond the 2TiB limit, for example"

There is no 2TB limit?

It all depends on the FS used. ext4 is ok for 16tb, i believe (on 64bit systems) - Btrfs can do exabytes.

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Re: Are there any size limits on USB hard drives?

Fri Aug 03, 2012 12:51 pm

I knew I read something some time ago :

http://www.raspberrypi.org/phpBB3/viewt ... tb#p132889


Texy
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RaTTuS
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Re: Are there any size limits on USB hard drives?

Fri Aug 03, 2012 12:57 pm

I'm using 640GB hd , 120GB hd and a 64GB SSD
all work at the same speed the ssd is for a very small pack that I'm making
http://www.suntekstore.co.uk/product-10 ... c_ssd.html <-ssd
http://www.amazon.co.uk/gp/product/B007HMDB4Q <- I use these USB to SATA adapters
if you want to rootFS on a partition on that drive then you will need a new kernel as it's drivers is covered by a module and not built into tthe kernel
but as a general store it works fine.
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johnlane
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Re: Are there any size limits on USB hard drives?

Tue Aug 21, 2012 8:00 pm

jdbennet wrote: There is no 2TB limit?
I was referring to the limit of addressible space using traditional MBR partitioning. I wasn't sure if you could use GPT on a USB drive on the Pi, hence the question.

I've since found another thread asking similar questions. It' be good to see something definitive on this if anyone has had success with drives over 2TiB.
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