P2 download times - maybe not 80MB/s?

ullanta

ullanta

Veteran
Sorry if this is improper, but I'm reposting this from the end of a long thread, ;cause i think it's worthy of beginning a new one, and I imagine many folks might be interested in the answers...

Basically, discussion here has all pointed to download times of around 1GB/minute from P2 to a laptop.

I've been thinking about this a tad, and it troubles me a tad. One minute per gig is around real-time; and about 17MB/s, or 133Mb/s.

The 100Mb/s of the HVX (~103 w/audio?) rate of live streaming is pretty darn close to this.

I wonder where the bottleneck is? I really don't feel so confident about capturing so close to the maximum throughput of the system, if the bottleneck is on the PC side.

However, I've tested and can transfer large files drive-to-drive over FW (400) at over 30MB/s. So I'm thinking the P2 bottleneck may lie either with Cardbus or... dare I say it... P2?

Can anyone with a camera and/or P2 card and two fast HDDs do a test to see where in the system the bottleneck lies? If you can transfer better than 17MB/s over firewire (or between internal and firewire, etc), but not from P2 to a drive over FW, then something on the P2 end (card or Cardbus) is the culprit.

Or, does anyone have a P2store? that should also be going significantly faster than realtime...

Finally, if anyone has, say, a Cardbus FW card and can confirm that it handles throughput higher than 17MB/s, it would help... I don't have one, but I think I've read reports that indicate speeds are competitive with internal FW800...

-Barry
 
The way to do it would probably be with a disk speed-check utility. That way you eliminate file transfer and overhead out of the equation and just compare the raw read/write speed.

Jarred has my cards right now, when I get 'em back I'll try to arrange such a test. Until then, hopefully someone else has one and can test?
 
Barry_Green said:
The way to do it would probably be with a disk speed-check utility. That way you eliminate file transfer and overhead out of the equation and just compare the raw read/write speed.
Click to expand...

I'd be interested in both... I really doubt (optimistically) that P2 can't spew at a higher speed, so it's possible there is something weird in "overhead"... like, maybe the P2 drivers? I don't know, and can't test... but I'd really like to see real world file transfer times more than a speed-check utility. As I say, I KNOW I can transfer at a sustained 30MB/s between FW drives...
 
We did some very extensive tests on transfers speed of P2 cards, in lab-conditions. Testing was done to compare different media ingest speeds. All testing was done in SD ( not HD). So, x-realtime indications refer to SD or 25Mbit. ( actually 30Mbit, see below)

2 kinds of test were done: Using the 5-card reader over USB2.0 and PCMCIA. There was a slight impact of cliplength to transferspeed: 10 short clips took a bit longer than 1 long clip. This because of FAT lookup overhead. The impact was actually minimal, certainly compared to XDCam.

The results:
USB2.0: between 7x and 9x realtime, or 220 and 250Mbit/s. I know, that makes realtime=30Mbit/s, but that's including all kind of metadata, sound,...

PCMCIA( P2 card in PCMCIA card reader in workstation): 11.5xrealtime for short clips, and up to 13x realtime for long clips.
Best time recorded was 395Mbit/s transfer speed.

This is of course still nowhere near the theoretical max of 640 Mbit/s. Bottlenecks are: the USB2.0 adaptor, the PCMCIA cardbus speed and HDD drivespeeds. + System overhead.

Just to show how good P2 actually is, compare it to XDcam, SONY's tapeless solution:
-P2 usb: 7x to 9x realtime SD transfer
-XDCAM firewire: 0.3x to 1.8x realtime ( !!!)

These are realworld tests, not theoretical numbers.

Panasonic is said to be working on a firewire-800 model of the P2 card reader. This would kill the USB bottleneck
 
eLeventy: just to be clear, can you tell us what you were capturing TO? What kinda HDDs and such... and, of course, THANKS for the useful info!

But, this indeed seems to make the 1GB/min transfers we hear about sound slow. Even thorough USB, you seemed to average 30MB/s or so... so why are people's reports of slower transfer? Is everyone using really slow HDDs?
 
So far everyone's using laptop hard disks, and those are slow. 3.5" hard disks in desktops typically have a lot higher throughput than most laptop hard disks.

Sending a card through PCMCIA to a 4-disk SATA raid should (SHOULD) result in the max transfer of 640mbps.
 
barry, i'm trying to avoid the firewire port at all costs for continuous recording so i'll have my powerbook w/ me. i'll be inserting the p2 card into the pcmcia slot and have a 7200rpm hard drive in a firewire bus powered drive connected to my laptop. will this be the fastest workflow for downloading the files into the firewire drive? is there a faster solution than this? thanks!
 
Barry_Green said:
So far everyone's using laptop hard disks, and those are slow.
Click to expand...

That's what I was suspecting, but haven't heard confirmed. I'd love to hear from someone actually using a decent FW drive...

BTW, as some of you may remember, I usually use and advocate Glyph drives, but have been having luck with an OWC Mercury-On-The-Go 7200RPM bus-powered Oxford-chip FW drive... I highly recommend it...
 
Well, there are certainly faster solutions, but none so practical. You should get about a minute per gig out of that situation. For faster you'd need something like a G-Raid or a G-SATA. Those won't be nearly as portable as a bus-powered drive though!
 
Barry_Green said:
Well, there are certainly faster solutions, but none so practical. You should get about a minute per gig out of that situation. For faster you'd need something like a G-Raid or a G-SATA. Those won't be nearly as portable as a bus-powered drive though!
Click to expand...


No way, man! I get sustained transfers of well over 30MB/s on the little bugger. That's why I use it... ProTools don't play well with most bus-powered drives, but loves this one. And, I'd assume, the new Glyph PortaGigs, but they're pricey and hard to get. Not just transfer rate, but seeking as well; it handles simultaneous transfers (e.g., multiple ProTools audio tracks and video) beautifully.

I ain't no fool.... I'm a Barry, too!
 
ullanta,

great to hear! i just ordered an on the go drive yesterday...always had good luck w/ their firewire solutions. thinking about getting their firewire raid solution over a g-raid since it costs less...or possibly a sata drive since there are sata pcmcia cards available now...

thanks barry g for the 411...
 
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