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WD 3.5" Caviar green as external HDD ?

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April 29, 2011 1:44:09 PM


Hi,

I use almost exclusively WD Caviar green 3.5" disks as internal storage on my desktop mainly because of their cool&quiet operation.

I'd like to know if it is possible, or if anyone has done it, to put these HDD (3.5" caviar green) on an external case with the following two important conditions:

1/ ONLY USB-powered; that is no other additional powering for my external case

2/ NO fan on the external case; that is the case body should be enough to cool the drive without any fan

The reason I don't consider 2.5" external disks which satisfy the above two conditions is simply because I want to reuse my internal disks that I already have as external additional disks.

If anyone has done it, I'd be interested to know since how long and on which case and if the case becomes hot or just warm.

thanks
nalooti
a c 379 G Storage
April 29, 2011 2:32:12 PM

1. I'm not aware of any 3.5" enclosure that doesn't need external power.

2. I use a vantec nexstar 3 enclosure with a WD 250G black drive which obviously uses more power and generates more heat than a green drive and even under load, the enclosure gets warm. The enclosure is aluminum, so it's suppoesed to get warm so that it can dissapate heat into the air, and away from the drive.
a c 415 G Storage
April 29, 2011 4:10:59 PM

I'm with Hawkeye22, I don't know of any 3.5" drives that are efficient enough to draw power through the USB bus.

I also use VanTec Nexstar 3 enclosures, and I've found that the green drives run considerably cooler in them than 7200rpm drive. I'd describe the 7200rpm drives as "hot" and the green drives as "warm".
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a c 302 G Storage
May 2, 2011 4:01:08 PM

Can't do it. USB 2.0 provides, at most, 500 milliamps at 5 volts. The Caviar Green 2 TB drive draws
Current Requirements
12 VDC
Read/Write 296 mA
Idle 243 mA
Standby 3 mA
Sleep 3 mA
5 VDC
Read/Write 503 mA
Idle 172 mA
Standby 160 mA
Sleep 160 mA

Even the 5V draw is slightly over, and there is no way that USB 2 can provide the extra 3.5 watts for the 12 volt line, even if you stepped it up with a voltage converter. That drive draws 2.43 times the power that is the max spec for USB 2.0.

In theory, you could look for a Powered USB case, if you had a Powered USB hub: http://en.wikipedia.org/wiki/Powered_USB

However, I just use these http://kingwin.com/products/cate/mobile/racks/kf_1000_b... to pop a bare external drive into my machine whenever I want to access it or back up to it. Much simpler, unless you have multiple machines or a laptop.

Let us know what you decide.
May 3, 2011 8:23:57 AM

Maybe, maybe not; I'd say it depends on the USB port and the MB.
According to : http://en.wikipedia.org/wiki/USB2
Max. current 500-900 mA @ 5 V (depending on version)

However it is possible that every current demand above 500 mA must be short (transient) otherwise the port couldn't provide it.

There is one way to make sure: to test it if anyone has a caviar green and a 3.5" enclosure (just don't power it on and see if it works).

There is more chance that the 1 TB version (drawing less power) could work.
a c 302 G Storage
May 3, 2011 1:02:45 PM

nalooti said:
Maybe, maybe not; I'd say it depends on the USB port and the MB.
According to : http://en.wikipedia.org/wiki/USB2
Max. current 500-900 mA @ 5 V (depending on version)

However it is possible that every current demand above 500 mA must be short (transient) otherwise the port couldn't provide it.

There is one way to make sure: to test it if anyone has a caviar green and a 3.5" enclosure (just don't power it on and see if it works).

There is more chance that the 1 TB version (drawing less power) could work.

900 ma at 5 V is 4.5 W, and is spec'ed for USB 3.0 anyway. The drive can draw 6 W. Going out of spec is risky, even if it works with one particular drive in one particular case. It may work one day, not work the next, and corrupt your data the third.

I had this experience with an out-of-spec 2.5" drive.

The 1 TB model specs state:
Current Requirements
Power Dissipation
Read/Write 5.40 Watts
Idle 5.40 Watts
Standby 0.40 Watts
Sleep 0.40 Watts

So my somewhat informed take is that it should not work, and if it does, it will not be reliable and should not be depended upon. Heck, I have a 2.5" external drive that requires the use of a Y cable to draw power from two USB ports. It has occasionally spun up on one port worth of power, but I would not use it that way.

Let us know if you find a counter-example.
!