Boot Disk: CF-IDE or USB key ?

[Evildead666]

I am currently installing an itx system in a CDRom burner case, and have had some knowledge of booting linux off CompactFlash-over-IDE and from USB Keys.

I have WinXP Pro installed on a 4Gb CompactFlash which states it is 100x speed.
Its Sooooooooooosooooooooooo soooooooooooooo slow !

This is on a Via Epia Mainboard with a 1GHz CPU and 512Mb of DDR.

The power supply is a Pico-PSU 60W, the size of the connector, just about twice as tall.
It runs off a 50W external 12V power supply which is warm, nothing more.

I have little knowledge of the actual interfaces, apart that the CF pins literally relate to an IDE connection in some way.
I'm not so sure about the number of I/O's per second, or in parallel, a CF interface or USB interface would be able to do.
The USB Key is a Corsair 4Gb device.

So, for a boot drive, which would be better overall:

The CF over IDE or the USB Key ?

Jez

[az]

Depends on their speeds, which do vary greatly. The fastest CF cards are Sandisk Extreme III AFAIK. Transfer rates for flash media are still much lower than for fast hard disks, but access speeds are a lot faster.

[spadnos]

Note that 1x is the native CD-reading speed, or 150k/second.

A 100x card can read 150k * 100 = 15 MB/sec, which is around 1/3 (or less) the speed of a modern hard drive. Even the 120x (the fastest CF I can think of) are only 18M/sec. This should still be fast for bootup, since the seek time is near zero.

Neither USB nor Compact Flash / IDE will limit the speed, the flash media will.

You should be sure to configure any OS to not use swap - that will be very slow and will wear out the disk rapidly.

- Steve

[Wombat]

More of IDE will be done by the hardware; USB is done largely by software. Therefore, I think CF would probably be faster/leave more processing power free.

[Dr Mordrid]

Aren you using a full Linux or one made for USB/Flash devices (DSL, DSL-N, CPXmini, SPB-Linux etc) ?

http://www.linuxlinks.com/Distributions/Mini_Distributions/

http://www.damnsmalllinux.org/

http://www.damnsmalllinux.org/dsl-n/

http://www.8ung.at/spblinux/

http://www2.informatik.hu-berlin.de/~bading/cpx-mini/

[az]

Oh, and manufacturers print all kinds of x-numbers on their flash cards, they don't always mean anything. Lexar are not bad, though as I said, the newest Sandisk extremes are faster. But I think the real difference will be in the software and how much your PC needs to access the flash, especially swap.

[Fat Tone]

Cosair Flash Voyager are generally the fastest USB keys around, with reported rates simillar to those Spandos quotes. My 1GB one was always impressing me. I just got a 4GB one and it took nearly an hour to transfer the stuff between them (via the HDD). Large files = fast, lots of small files = slow. Maybe thats an OS thing.

[Evildead666]

I've installed XP Pro onto a 4Gb CF.
That is what i've bought the 4Gb USB Key for also, to see if there is a noticable difference.
I looked at the boot process, and i think the xp boot process switches off the USB for a short time, then restarts it.? So it may not be possible on USB at all...

For Linux, i was just saying that it was always fast when i did some tests, and made a firewall router dhcp server from a via epia booting off CF. I suppose it was command line so i can't really compare...

[Evildead666]

Basically, I thought a CF card was basically made to read or write ONE thing at a time, like for a Digital camera, or simple storage. I'm worried that the CF cards themselves are not up to it in the concurrent I/O sector..
They are only just announcing 8-16Gb flash devices compliant with the Windows Vista Cache thingy...

If i try to do two things at once, for example, the computer will "think" for a very very long time.
I am sure its from the HDD choice (CF over IDE) but i've tried two different cards, and i get the same speeds. Boot process seems ok, but program usage and stuff sucks badly, menus, everything needed for Windows.

[Wombat]

I think flash in general (USB or CF) isn't really optimized for random read/write accesses.

Can you disable swap on your system?

[spadnos]

Hmmm. I forgot about the USB handoff.

When the BIOS is configured for "USB Legacy Support", it can boot from USB, but when the OS loads its driver, there's a specific handoff method (which I don't know). That can cause access to be interrupted while the driver is loading. That shouldn't be a problem, unless some OS tries to load multiple drivers simultaneously, and happens to turn off USB while something else is trying to load.

Regarding random access, I'd imagine that a flash card is excellent for that. The seek time is on the order of microseconds (to set up the memory addresses on the card), and as long as you're reading roughly the page size, the transfer rate should be the same speed as sequential reads.

This is theoretical information, however, so real life may prove me wrong

Here's a reasonably priced IDE flash hard disk module:

http://www.intellesale.com/item.asp?referid=161160&id=85817

- Steve

[Evildead666]

Big spanner in the CF-IDE, this one is only detected in PIO mode.
I'm pretty sure thats the problem.

I'm now trying the Corsair 4Gb USB Key that arrived this morning

I'm pretty sure my other CF6IDE device made DMA at least...gonna do a swap later if this is just as slow.

edit: Interesting link spadnos, i hadn't realized they'd gotten so big now ....

[Evildead666]

Nope, changed the CF-IDE adapter and still the same...
USB Won't boot XP. Even thought it will with Linux...

Maybe i'll go for a 2GB Sandisk Ultra 4 233x CF Device, or just bugger it and use a real 120W µATX PSU...
Just trying now with a 80Gb IDE Drive...

[az]

why not a 2.5" laptop drive? They're quiet, use little power...

[Evildead666]

I don't have any laptop drives lying around, and i would need an adapter to get it to work...
I have asked around for a laptop drive, and am waiting for the replies...maybe this week...

It IS a lot lot lot faster running off the HDD though...