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Thinking of Building an External USB Drive Array

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July 16, 2005 3:27:51 PM

A friend of mine and I are thinking about building an external USB (or could be firewire) drive array.

Here's what we're thinking: We both have a need to have some good size portable storage. I have five computers; two at home and three at work. Occasionally I need to be able to move large amounts of files off of them (or more accurately between them). I bought a USB 2 external hard drive enclosure and put a 7200rpm 250GB PATA drive in it. Unfortunately as is often the case, I filled this sucker up pretty quickly, so this defeated the purpose of having another drive. What I really need is more space and a way to access it all at once from any machine.

This got me thinking. I could build another PC and make it a server, but that's overkill and would cost too much. Why not just use the internal parts from several of these external enclosures (the part that converts the hard drive to USB), get a small cheap case with a small psu (which I could hook up to the drives), get some cooling fans, and get a USB hub (to plug all the drives into). Then I would have a box with say four or more drives in it that could run to the USB hub. I could have two cords coming out the back, one for the hub and one for to plug into a USB port on whatever computer I would use. It would be pretty simple and not cost much to build. I could add drives on a need by need basis even!

The usb to ide part I was thinking of using would be something like this: http://computerlogin.com/onwa/Whole...IDEAdapter.html
only I wouldn't need the external power (since I'd be using a PSU). I could probably find these somewhere for under $5 each...

A couple of questions I have are:

1) Would the PSU work if it's not connected to a motherboard?

2) I'm not sure how I could hook the hub up inside of the case (or are there hubs that you can buy that go inside of cases?)

3) How to hook the hub up to the PSU's power.


Anyway, I'd like to get other people's opinions on this. I'm sure someone has build something like this before. I'd like to learn from them and get your ideas on the best way to do this.

Feel free to tell me that this would work (if it wouldn't) or make suggestions on a better idea if you've got one. I'm basically looking for cheap, somewhat portable storage, but I don't want to have a bunch of USB external enclosures where I have to plug each drive in.

Thanks.
July 22, 2005 1:13:20 AM

This is a really bad idea. I would recommend PATA enclosures with USB/SATA bridgeboards like the Raidsonic 'Icybox' range and others. Don't rely on USB 2.0 alone...!!

Going with USB alone is a bad idea as well because it really limits the speed of your HDs. They are already slow enough without limiting them to a maximum transfer rate which will be much below the maximum 480Mbit/s with overheads. You'll also get a big CPU hit when you start accessing the drive.

I've tried Firewire 800/IEEE1394b and the driver was unstable under Windows XP (haven't tried IEEE1394b under Service Pack 2 yet :-). However the bridgeboards make the enclosures __very__ expensive. At the end of the day this interface isn't that fast unless you have a PCI-X slot/64-bit/66Mhz+ IEEE1394b card. Also although you can have as many HD as you like all the chained HD share the same 800mbit bandwidth.

A cheap multiway SATA card+breakout connector+external SATA/USB enclosures is the only way to get a decent external disk setup. E.g. my setup is Supermicro PCI-X 8-port SATA card + 8-port break PCI slot - 'Macgurus' do this (when will PC manufacturers catchup with Sonnet for the Mac and do a PCI/PCI-X card with 4/8 external ports for Windows/Linux!!) + Raidsonic SATA(SATA) and SATA/USB(PATA) external enclosures... The Supermicro SATA card is useable in an ordinary 32-bit PCI slot (just now :-) and works fine (well except for a problem with TCQ - tagged DMA command queuing that I am working to sort out)

So in summary USB external drives are fine for backup and transfering files between computers. You can't treat them as useable for File-serving (unless you have an Athlon 2x to devote 1 core to the USB CPU load!!) or for workspace for you PC - too slow and too much CPU load again... With my minor niggles with TCQ I was running my SATA/USB enclosures on USB and its like everything went into slowwww-motion....

NCQ in SATA is also worth considering. Windows is completly lame when it comes to any kind of file transfer. Try moving a large file to a ATA disk and then transfer another large file to the same disk. Windows will start thrashing the disk and both transfers will grind virtually to a halt. Now try this with a U160/320 SCSI or NCQ SATA harddisk (with NCQ enabled Host controller) you should see a big improvement in performance!! Many newer SATA HD provide NCQ as standard.. as does the older flagship WD 74Gb Raptor (the flagship of SATA drives :-)... the drive I use when building PCs for folk!!

BTW I speak from the voice of bitter experience :-)

Robert
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