Thanks, Igor - I guess I misunderstood what I read about PCIe x1. I had
the impression that adding a USB 3 card would be futile. I'll give the
add on card a try - some of the 2TB drives I will be using in the send
copy of the backup at USB 2 so they won't benefit from the speed up, but
the newer / larger 3 TB drives will.
Mark
On 10/29/2014 11:21 AM, Igor PDML-StR wrote:
Mark,
First of all, - just in case: there might be a confusion between the
width of the bus in number of lanes (PCIe x1, x4, x16...) and the
version of the PCIe (1.0a, 1.1, 2.0,..)
See, e.g. this Wikipedia article that summarizes it nicely:
http://en.wikipedia.org/wiki/PCI_Express
So, the Transcend card for $13 that I mentioned (see below) is suitable
for PCIe (x1). I am not 100% which versions of PCIe (1.1, 2.0) it is
compatible with, but as far as I can tell from the age of my Desktop,
the PCIe in it is ver. 1.1, and that card is working. And what is more
important, it gives a very substantial speed increase over USB 2.0
with the same external HDDs.
You are right, the lane bandwidth in PCIe pre-v.2.0 is 2Gbit/s (250
MB/s),
which is less than the theoretical maximum rate of USB 3.0, but
I am yet to see any of the external USB 3.0 HDD to utilize the full
bandwidth of the USB 3.0.
I don't remember the numbers, - but in my configuration (that seems
like what you might have), I was getting sustained rates in the
vicinity of 100 MB/s (definitely above 80 MB/s), while I was happy if
I'd get over 20 MB/s
[sustained!] with USB 2.0 with the same drives.
So, for the price of $13, it was worth it, don't you think? ;-)
As I mentioned earlier, another limitation for PCIe x1 is the power.
It only matters for the USB-powered HDDs. I don't remember numbers
right now, but it is sufficient for at least one or even two USB drives.
At least my USB-powered drives work just fine.
And BTW, - about a month ago, I bought this USB 3.0 card reader (Yet
another $13):
http://www.amazon.com/Transcend-Super-Multi-Card-Reader-TS-RDF8K/dp/B0056TYRMW/
Copying files from the SD cards speeded up 3-10 times, depending on
the card.
Actually, im my testing, the sustained rate went 50-100% up even
if this reader is used with a USB 2.0 port, as my highest sustained
rate with USB 2.0 reader was at about 13-15 MB/s, and with this reader
and USB 2.0 port, it is around 20 MB/s. With a USB-3.0, I am getting
the sustained rate of 32-33 MB/s on my laptop, where, I suspect it
might be limited by its USB 3.0 card.
Mark, sorry for pushing on you some spending ideas. ;-)
... but at least they aren't as costly as any of the lenses... ;-)
Cheers,
Igor
Mark C Wed, 29 Oct 2014 07:14:51 -0700 wrote:
Thanks, Igor - I looked into adding a USB 3 card and found that the
only available slots on my PC are PCIe x1 - which I think is too slow
to support USB 3.0. Maybe I don't understand the specifications
correctly - I think PCIe 2.0 is needed.
Mark
On 10/28/2014 10:38 PM, Igor PDML-StR wrote:
Mark,
Just in case, - since you mentioned you were considering a USB 3.0
card, - Two years ago, I bought this card:
http://www.bhphotovideo.com/c/product/696114-REG/Transcend_TS_PDU3_2_Port_USB_3_0_PCI.html
I put it into my desktop that was put into "production" back in
January of 2007. I am not using this desktop as frequently as my
laptop, but I have some software on it that is not available
elsewhere, and so, it is very nice to be able to use the same HDDs
efficiently.
I don't remember if you are using a Mac or PC, but if it is a PC,
$13 is not that much to get a much better experience.
Cheers,
Igor
PS. There are more expensive cards with that have more than 2
ports, but those are (1) more expensive, and (2) they have some
additional limitations due to the PCI-e. However, if you've got an
empty PCI-e x4 (or x16) slot, I suspect you can buy something that is
even better. Also, note that the card referenced above may not
adequate power to power some "mobile" HDDs that are USB 3.0-powered
(and require 0.9V). For those, you need a card with an additional
power connector (from the power source or elsewhere). If you have any
questions on this, - feel free to ask me.
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