[kwlug-disc] USB3 expectations?

Steven Stillaway steve at stillaway.net
Mon Jun 21 06:26:51 EDT 2010

It is recognized as USB3, but as I said, I have no USB3 devices to test 
it with (my assumption of the "noSuperSpeed" comment).  Notice it is 
"xhci_hcd" rather then "ohci_hcd".

[   22.397278] xhci_hcd 0000:07:00.0: PCI INT A -> Link[LNND] -> GSI 19 
(level, low) -> IRQ 19
[   22.397305] xhci_hcd 0000:07:00.0: setting latency timer to 64
[   22.397309] xhci_hcd 0000:07:00.0: xHCI Host Controller
[   22.397397] xhci_hcd 0000:07:00.0: new USB bus registered, assigned 
bus number 3
[   22.397537] xhci_hcd 0000:07:00.0: irq 19, io mem 0xfe7fe000
[   22.397576] usb usb3: config 1 interface 0 altsetting 0 endpoint 0x81 
has no SuperSpeed companion descriptor
[   22.397646] usb usb3: configuration #1 chosen from 1 choice
[   22.397651] xHCI xhci_add_endpoint called for root hub
[   22.397653] xHCI xhci_check_bandwidth called for root hub

USB3 is indeed supported in the kernel.  You will have to check for 
support for an individual chipset depending on your controller though, 
as there is more then one, but as long as the manufacturer has 
co-operated with the kernel people, I imagine any chipset will be 

One of the advantages USB3 will have over SATA is that it is a serial 
port.  You will be able to daisy chain multiple devices to the one port, 
which you cannot do with SATA.  Also hotplugging will work better with 
USB3 then it does with SATA.  There may be other advantages as well, I 
am not sure.

In terms of pure speed SATA may likely be better though -- I believe 
there are some speed tests of USB3 out there that you could search 
online for.

I don't think the goal of USB3 was to compete with SATA, it was just to 
make faster USB.  It will be use full for many things other then just 
plugging in disks (video?).

- Steven

On 06/19/2010 11:00 AM, Chris Irwin wrote:
> On Fri, 2010-06-18 at 21:07 -0400, unsolicited wrote:
>> But, vis a vis eSata, why go down the USB road? OK, I know, no eSata
>> port. But also, likely, no USB3 port.
>> Internally, be it internal flash drive or bay, you know it's going to
>> be SATA based, not USB based.
>>> SATA-III will also benefit "Small" virtualization users with
>>> on-host storage. "Big" virt users will have centralized network
>>> storage (and thus still benefit according to your rule above), but
>>> us smaller guys running multiple VMs locally will potentially see a
>>> benefit.
>> Right, I get the whole SATA III thing, if drives are a bottleneck,
>> it's the USB3 thing that nobody's said 'Why?' over eSata, yet.
> I don't have an answer. I think eSATA will be faster, but whether or not
> you actually need that speed.... One of the big benefits of USB is that
> it is used for more than just storage. But what else needs to transfer
> that much data? Video&  Still cameras are glorified mass storage
> devices...
> I wonder if we'll see USB3 "RAM" extenders. Plug it in and it holds your
> swap...
>>>> - even on a home connected web server, the limitation will be ISP
>>>> speed, not disk speed? IIRC, typically systems are disk bound,
>>>> but there's a whole lot of 'stuff' between the CPU and disk,
>>>> preventing an increase in disk speed from providing an equivalent
>>>> increase in system speed? (And this is even presuming sufficient
>>>> requests are coming in sufficiently often to "make 'it'
>>>> worthwhile"?
>>> I use unison to sync $HOME between my laptop and server. It runs on
>>>   both local and remote hosts, examines my data on each, then
>>> presents a merge-list (which it executes using an rsync-like
>>> method). The part where my two $HOME directories are being examined
>>> takes more time (by far) than the actual data sync over the network
>>> (even using wifi). Faster disks on my server, even given the 'slow'
>>> network link, would still be a benefit.
>> Hold on, is the issue there disk speed, or CPU speed calculating the
>> deltas?
> I'd say disk speed. I have an SSD in my laptop, and unison indicates it
> is waiting for the remote
>>>> - if drives are SATA, and the bus is USB3, why USB3 instead of
>>>> just staying with (e)SATA?
>>> Getting a USB3 enclosure for your drive would allow backwards
>>> compatibility with USB2 hosts -- granted, most eSATA enclosures
>>> also have USB2.0 ports anyway. Some SATA chipsets don't like hot
>>> unplugging.
>>> eSATA drives need a separate source for power, versus one
>>> power+data cord for USB.
>> Right, but your .jpg above shows that ain't necessarily so.
> The only problem is: when can you assume people have that? I still see
> laptops that come exclusively with VGA output, nevermind DVI, HDMI, or
> DisplayPort.
>> So, the USB / firewire 'next level' race is back on, but joined by
>> eSata now.
> The fight is on for storage devices. USB already won everything else. I
> don't see firewire going after they keyborad/mouse/webcam connector
> market.
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