USB 3.0 SATA Hard Drive Docking Station


8 posts
by marcelp1 » Wed Jul 04, 2012 7:32 pm
Hi,

did anyone test the RPi with HDD Docking Station?
I have http://www.maplin.co.uk/usb-3.0-sata-ha ... ion-588968
and wonder if I buy 2TB SATA HDD for it, if it would work with RPi ..........

Thanx in advance.
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by scorp » Wed Jul 04, 2012 7:42 pm
I recall someone complained on USB-3.0 HDD although being compatible with 2.0
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by CCitizenTO » Sat Jul 07, 2012 5:25 pm
I think people are disappointed with USB3.0 peripherals on the RPi because to maintain compatibility they will fall back to USB2.0 speeds thus they wont get the same performance out of them as they would if they hooked them up to their newer desktop or laptop machines that have a USB3.0 port.

Chart of USB Speeds
USB1.0: 15Mbps (1.88MB/s)
USB2.0: 480Mbps (35MB/s)
USB3.0: 5Gbps (625MB/s)

Chart of SATA Speeds
SATA1: 1.5Gbps (0.19GB/s)
SATA2: 3Gbps (0.34GB/s)
SATA3: 6Gbps (0.75GB/s)

Also I dont think the Pi can handle speeds like 5Gbps. Which is probably why it does not have a 1Gbps Ethernet Adapter (aside from cost considerations as well). That said I've never managed to download something faster than maybe 100-200MB/s on my connection to the internet so that doesnt really matter.

Also you have to keep in mind that conventional drives (rotating spindle) have hit their peak in terms of data throughput. They are big, inexpensive but SLOW. SSDs are small, expensive but FAST. This is ofcourse assuming the same pricing points. There are 2TB SSDs out there that cost you an arm and a leg.

It may just be you have a USB3.0 SATA dock laying around or a USB3.0 one cost as much as a USB2.0 one. But functionally working with the Pi and working with conventional drives they're equivalently the same because it wouldnt take advantage of the higher speeds USB3.0 has to offeranyways.
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by obarthelemy » Sat Jul 07, 2012 9:15 pm
Those speeds are extremely theoretical:

1- both interfaces have overhead, USB a lot more than SATA. So that 480 Mbps pipe really doesn't ever deliver more than around 350 of useful data.
2- USB uses a lot of CPU cycles to manage the connection and handle the data. Someone's noticed that even with just a keyboard and mouse connected, USB handling uses up to 20% of the Pi's CPU cycles. That's with only 2 peripherals, and very little data to handle. The current USB driver is ... not very good.. but building a better one seems hard.
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by CCitizenTO » Sun Jul 08, 2012 5:29 am
obarthelemy wrote:Those speeds are extremely theoretical:

1- both interfaces have overhead, USB a lot more than SATA. So that 480 Mbps pipe really doesn't ever deliver more than around 350 of useful data.
2- USB uses a lot of CPU cycles to manage the connection and handle the data. Someone's noticed that even with just a keyboard and mouse connected, USB handling uses up to 20% of the Pi's CPU cycles. That's with only 2 peripherals, and very little data to handle. The current USB driver is ... not very good.. but building a better one seems hard.


I believe part of the problem on the Keyboard/Mouse may be how inputs or interrupts are handled. Basically each cycle or so the CPU asks the keyboard/mouse if it has anything for it to process. Much like kids on a road trip 'ARE WE THERE YET?' :P
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by marcelp1 » Sun Jul 22, 2012 1:44 pm
CCitizenTO wrote:I think people are disappointed with USB3.0 peripherals on the RPi because to maintain compatibility they will fall back to USB2.0 speeds thus they wont get the same performance out of them as they would if they hooked them up to their newer desktop or laptop machines that have a USB3.0 port.

Chart of USB Speeds
USB1.0: 15Mbps (1.88MB/s)
USB2.0: 480Mbps (35MB/s)
USB3.0: 5Gbps (625MB/s)

Chart of SATA Speeds
SATA1: 1.5Gbps (0.19GB/s)
SATA2: 3Gbps (0.34GB/s)
SATA3: 6Gbps (0.75GB/s)

Also I dont think the Pi can handle speeds like 5Gbps. Which is probably why it does not have a 1Gbps Ethernet Adapter (aside from cost considerations as well). That said I've never managed to download something faster than maybe 100-200MB/s on my connection to the internet so that doesnt really matter.

Also you have to keep in mind that conventional drives (rotating spindle) have hit their peak in terms of data throughput. They are big, inexpensive but SLOW. SSDs are small, expensive but FAST. This is ofcourse assuming the same pricing points. There are 2TB SSDs out there that cost you an arm and a leg.

It may just be you have a USB3.0 SATA dock laying around or a USB3.0 one cost as much as a USB2.0 one. But functionally working with the Pi and working with conventional drives they're equivalently the same because it wouldnt take advantage of the higher speeds USB3.0 has to offeranyways.


Thanx for your reply.
I have instead used Seagate Expansion External 2TB USB Drive. Formatted in NTFS so I can in case that RPi does not work straight into Windows XP machine.

But the speed of writing any files to the HDD is so slooow. I have connected both HDD to the USB ports and in MC try to shift some +1GB files between the 2 disk (both NTFS) and that was so slow.
But as s sort of NAS the RPi works perfect.

Could SATA or IDE HDD be attached to RPi?
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by obarthelemy » Sun Jul 22, 2012 4:22 pm
"Much like kids on a road trip 'ARE WE THERE YET?'"

I had missed that one.

OTOH.. I didn't *miss* it...
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by phbcanada » Tue Dec 11, 2012 8:21 pm
Apparently the ntfs driver is very slow (something to do with fuseblk type). Don't use it if you want good performance. Try ext4 on your hard drive.

Did you get the sata + dock working?
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