What i'm wondering is if one could setup a linux installation on usb drives that are in a RAID 0 config.

3/23/2006 7:56:56 AM

yes, its already been done

3/23/2006 7:01:12 PM

yeah, i was looking to see if someone could point me somewhere (ie a project page or something).

3/23/2006 7:06:23 PM

the question is, why? They are still ass slow

3/23/2006 7:18:44 PM

USB has way too much CPU overhead to be efficiently used for RAID. The only way to do it would be to have the RAID array hardware controlled and connected the the PC without the PC even "knowing" it's RAID.

Trying to RAID USB drives would be ... counterproductive...

You would end up with a slow array that has a high failure risk and high CPU demand.

[Edited on March 23, 2006 at 7:23 PM. Reason : "counterproductive" = stupid]

3/23/2006 7:21:37 PM

not to mention you are severely limited by the USB2.0 bus

3/23/2006 7:27:47 PM

I don't see how you are limited by the USB2.0 bus.

3/23/2006 8:21:11 PM

then you don't understand usb2.0, or the fact that it resides on the pci bus. or the fact that it shares its bandwidth across devices.

3/23/2006 8:35:52 PM

Okay. I am going to try to explain this in the simplest way possible.

The USB2 resides on the PCI bus which is controlled by the chipset's south bridge. The south bridge does not have as much of the CPUs "attention" as the north bridge does. There is a limited number of clock cycles that the PCI bus has to work with and any device on it gets a subset of that allocated bandwidth.

Now, the USB2 root hub has 480 megabits per second worth of bandwidth allocated to it. Any device on that root hub gets a subset of that bandwidth.

We are talking about megaBITs per second so to get megaBYTEs per second we have to divide by 8. So...

480 Mbps / 8 = 60 MB/sec

So the ABSOLUTE MAXIMUM speed of any USB2 drive is 60 MB/sec.

The maximum speed of any attached drive is 1/n where 'n' is the number of drives.

So ...

 # Drives        MAX Speed/Drive
-----------   --------------------
     1             60 MB/sec
     2             30 MB/sec
     3             20 MB/sec
     4             15 MB/sec
     5             12 MB/sec

3/23/2006 9:44:18 PM

granted that's max speed per drive if ALL are being accessed at the same time.

for good old storage purposes a raid usb setup might be ok.

3/23/2006 10:22:47 PM

If it's RAID then they will be accessing at the same time. He said RAID 0, so any file of significant size would require multiple stripes across all drives.

(How in the hell can you have RAID where only a single drive is accessed?! In that event it would not be RAID.)

RAID 0 ONLY offers performance as a selling point but in the case of a USB setup the advantage is completely nullified. Not only is there no advantage, there is also the HUGE disadvantage of catastrophic data loss if any single drive in the array fails. RAID 0 offers no redundancy.

[Edited on March 23, 2006 at 10:38 PM. Reason : it's how RAID works, durr]

3/23/2006 10:31:36 PM

thats why you RAID 5 or RAID 0+1

3/23/2006 10:38:58 PM

^ yep!

... but not with individual USB drives.

3/23/2006 10:55:41 PM