USB2 - Card or Hub?

  • Thread starter Thread starter Talal Itani
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Talal Itani

I need more USB2 ports on my PC. Is an internal PCI card a better choice,
than an external Hub? I want to connect up to 7 or 8 USB2 drives to the PC
and transfer data to the drives in batch. Thanks.

T.I.
 
Talal Itani said:
I need more USB2 ports on my PC. Is an internal PCI card a better choice,
than an external Hub? I want to connect up to 7 or 8 USB2 drives to the PC
and transfer data to the drives in batch. Thanks.
Click to expand...

I doubt you'll find a PCI card with 7 or 8 ports, so you'll need a hub
anyhow...
 
I need more USB2 ports on my PC. Is an internal PCI card a better choice,
than an external Hub? I want to connect up to 7 or 8 USB2 drives to the PC
and transfer data to the drives in batch. Thanks.

T.I.
Click to expand...

If you are going to be using more than one device on the hub at a
time, then realise that they will be sharing bandwidth. This is ok for
low bandwidth devices like mice and keyboards, but not a good idea for
drives and other high bandwidth devices.

If that is the case, go with a card and give each high bandwidth
device its own channel.

Dean G.
 
I need more USB2 ports on my PC. Is an internal PCI card a better choice,
than an external Hub? I want to connect up to 7 or 8 USB2 drives to the PC
and transfer data to the drives in batch. Thanks.
Click to expand...

Apart from the bandwidth contention mentioned by ano poster when
using a USB hub, it's also the case that small USB plug-in devices
(eg digital cameras and MP3 players etc) draw their power from the
USB hub without the hub needing its own power supply. But external
HDDs would definitely need a hub with its own power supply ...so I'd
go for internal USB card(s) which can draw power from the PCI bus.
 
Apart from the bandwidth contention mentioned by ano poster when
using a USB hub, it's also the case that small USB plug-in devices
(eg digital cameras and MP3 players etc) draw their power from the
USB hub without the hub needing its own power supply. But external
HDDs would definitely need a hub with its own power supply ...so I'd
go for internal USB card(s) which can draw power from the PCI bus.
Click to expand...


Unless the USB drives are notebook (2.5" or smaller) they
have their own power source, supply, do not require
significant power from the hub in most cases.
 
I need more USB2 ports on my PC. Is an internal PCI card a better choice,
than an external Hub? I want to connect up to 7 or 8 USB2 drives to the PC
and transfer data to the drives in batch. Thanks.

T.I.
Click to expand...


Already answered, quit being an ass.
 
Talal Itani said:
I was thinking about two PCI cards.
Click to expand...

You can do that, if you want.

Just remember that the bandwidth will be limited by the PCI bus to 133 MBps
total for the bus, so don't expect full bandwidth when you're transferring
across several drives at one time.
 
hummingbird said:
Apart from the bandwidth contention mentioned by ano poster when
using a USB hub, it's also the case that small USB plug-in devices
(eg digital cameras and MP3 players etc) draw their power from the
USB hub without the hub needing its own power supply. But external
HDDs would definitely need a hub with its own power supply ...so I'd
go for internal USB card(s) which can draw power from the PCI bus.
Click to expand...

I don't know what the power limitations are from the PCI bus, but I suspect "7
or 8" HDs drawing all their power from the USB port would overtax the USB power
lines. A single 5400 RPM, 2.5" notebook HD such as the WD Scorpio draws the
2.5 watt (500mA at 5 V) max allowed via the USB port, and the startup current
required for a Seagate 7200 is 1.1 amps, more than twice the limit.

However, all USB HDs I've used have their own external power supplies, so it
probably won't make any difference.
 
Unless the USB drives are notebook (2.5" or smaller) they
have their own power source, supply, do not require
significant power from the hub in most cases.
Click to expand...

My own external WD HDD has its own power supply. But there are USB
drives which don't. The OP made no mention of which type he plans to
use and attaching eight external drives through a USB hub looks like a
Heath Robinson affair to me, hence my comments.
 
I don't know what the power limitations are from the PCI bus, but I suspect "7
or 8" HDs drawing all their power from the USB port would overtax the USB power
lines. A single 5400 RPM, 2.5" notebook HD such as the WD Scorpio draws the
2.5 watt (500mA at 5 V) max allowed via the USB port, and the startup current
required for a Seagate 7200 is 1.1 amps, more than twice the limit.
Click to expand...

To attach 8 HDDs one would need to use several USB adaptor cards each
taking up one PCI slot. Wouldn't that spread the load?

However, all USB HDs I've used have their own external power supplies, so it
probably won't make any difference.
Click to expand...

I believe most do but not all.
 
hummingbird said:
My own external WD HDD has its own power supply. But there are USB
drives which don't. The OP made no mention of which type he plans to
use and attaching eight external drives through a USB hub looks like a
Heath Robinson affair to me, hence my comments.
Click to expand...

I should have said, that I plan on attaching flash drives, sd and mirosd. I
need to write to them in batch. These drives are not very fast, so I think
the speed limitation is in the drive, and not the USB. I do not know for
sure. I plan on trying things this weekend, to find out.
 
hummingbird said:
To attach 8 HDDs one would need to use several USB adaptor cards each
taking up one PCI slot. Wouldn't that spread the load?



I believe most do but not all.
Click to expand...

ok. These are flash memory drives. sd and microsd. They are slow, and
they do not consume much power.
 
I should have said, that I plan on attaching flash drives, sd and mirosd. I
need to write to them in batch. These drives are not very fast, so I think
the speed limitation is in the drive, and not the USB. I do not know for
sure. I plan on trying things this weekend, to find out.
Click to expand...

It doesn't work like that. You can't just assume that if
one bottleneck is lower than another, that the other won't
still effect the first. Often they are a cumulative effect
and especially so on USB as it can tend to be high latency.

If you have very old and low end drives, yes they may not be
bottlenecked much, but it would still be a bottleneck if
trying to do concurrent IO to all simultaneously on a hub.
Maybe your motherboard or the card reader controller is very
slow and that too is a bottleneck, so we cannot tell you
that merely choosing a hub or cards is the only variable
involved, but it is a significant one in achieving max
possible speeds.

If they are fairly modern middle-or-higher performance flash
drives/cards/etc, a USB2 hub is going to be a performance
bottleneck. One definite bottleneck present among many
possible bottlenecks that may or may not also exist.
 
Talal Itani said:
I should have said, that I plan on attaching flash drives, sd and mirosd. I
need to write to them in batch. These drives are not very fast, so I think
the speed limitation is in the drive, and not the USB. I do not know for
sure. I plan on trying things this weekend, to find out.
Click to expand...

Depending on your physical layout, a hub or 2 may be more convenient, rather
than having to access the back of the machine to swap out card readers.
 
Depending on your physical layout, a hub or 2 may be more convenient, rather
than having to access the back of the machine to swap out card readers.
Click to expand...


Why would you need access to the back of the machine?

With a reader having integral USB plug, you could use a USB
extension cord. With a reader having a common USB socket to
connect to a miniplug, that too is still an extension cord
and could be swapped if necessary. Also, if these card
readers did have integral USB plug, like a thumbdrive style,
it may require more hubs that the # of ports per hub would
suggest as it may not be possible to concurrently plug two
into adjacent sockets simultaneously as their physical
casing size is too large. Extension cords would again
become useful.
 
kony said:
Why would you need access to the back of the machine?
Click to expand...
With a reader having integral USB plug, you could use a USB
extension cord. With a reader having a common USB socket to
connect to a miniplug, that too is still an extension cord
and could be swapped if necessary. Also, if these card
readers did have integral USB plug, like a thumbdrive style,
it may require more hubs that the # of ports per hub would
suggest as it may not be possible to concurrently plug two
into adjacent sockets simultaneously as their physical
casing size is too large. Extension cords would again
become useful.
Click to expand...

Extension cords cost $$.

Hubs come in MANY more useful configurations than do PCI cards. He could
shop around for a pair of hubs that will accommodate his card readers
directly.
 
ok. These are flash memory drives. sd and microsd. They are slow, and
they do not consume much power.
Click to expand...

In this situation I think which route you go becomes largely down
to cost and/or convenience. For a permanent set-up, I'd certainly
go for the internal USB card(s) solution.
 
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