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Barry_Green
04-18-2008, 10:37 PM
Okay, I can't believe it's taken me this long to get this one out, but with everything going on I kept forgetting to write this one up. One of the great things about NAB is that you can hunt down the engineers that build this stuff, and get info straight from the horse's mouth. And what I found out about P2 I thought a few of you might find a little interesting!

I wanted to know a) why P2 is more expensive per gigabyte than other memory cards with high performance, and b) why the write speed seems slower than the read speed. I mean, all SD memory is usually slower when writing than it is when reading, but it seems like it takes longer to write to a P2 card than it should. Something didn't quite add up, and I wanted to find out why.

Get this: it turns out the microprocessor in the P2 card is doing quite a bit more than a simple RAID 0 function. It actually WRITE VERIFIES every bit that gets recorded to the card! So, when it comes time to record, the P2 controller receives a byte from the camcorder, and it writes it out into the SD memory card. It then READS that byte back in, to verify that it got written out accurately. If there's a discrepancy, it tries writing again, and reading again. It can do this process up to six times before it has to mark that byte or that page as "bad" and move on to the next sector. P2 was overengineered in the first place to provide massive write speeds (640mbps) to take factors like this into account. So, with a maximum data stream of 100mbps, the P2 card can try and retry up to six times before it needs to move on.

This gives you absolute certainty that your data has been recorded flawlessly and that when you read it back, it'll be exactly what you intended. Ultimate reliability.

So, next time someone whines about how "P2 is just some SD cards raided together", perhaps now we can point out that there's a whole lot more going on under the hood. Panasonic bet the company on this P2 strategy, and they appear to have taken it very seriously to make sure that it'll perform perfectly each and every time.

And, yes, this functionality is included in the P2 card itself, not in the drivers or in the cameras or anywhere else. So no matter where you use the card (in a laptop, P2 Gear, P2 Mobile, a camera, a Duel Adapter, anywhere) you know you're getting this reliability.

Zander
04-19-2008, 09:30 AM
That's fantastic. Thanks Barry.

Jim Brennan
04-19-2008, 01:43 PM
I wonder how that compares to the cards in the Sony....:evil:

cici
04-19-2008, 01:55 PM
I wonder how that compares to the cards in the Sony....:evil:

Me too... but not only rhetorically.... I'd really like to know about :)

Jim Brennan
04-19-2008, 09:25 PM
I used to complain about the P2 cards being proprietary, but now I see the sense in Panny's method. A lot of challenges with a cheap card can be blamed on the camera.

Interesting thing though. When I saw the guys at Hoodman and asked about their line of P2 cards, they said they dropped the idea, and that "there was no future in it for them" anyone have any insights on that?

TedRR
04-19-2008, 10:30 PM
Funny that Panasonic isn't flaunting this, especially since Sony is bragging so hard on the "simple" SD card recording. I don't think this would stop me from ever using the Sony camera, but it's nice to know how safe my P2 data really is.
Thanks Barry.

Barry_Green
04-19-2008, 10:32 PM
When I saw the guys at Hoodman and asked about their line of P2 cards, they said they dropped the idea, and that "there was no future in it for them" anyone have any insights on that?No... but Fuji introduced their lineup of P2 cards at about the same time. Perhaps the two announcements were related?

Maybe Fuji's announcement took the market slot that Hoodman thought would be theirs, as the "alternative" manufacturer? Or, maybe Hoodman found it tougher to produce a clone card than they thought it would be (and maybe it's because the P2 card does a lot more than we thought, like write verification)? Spec-Comm at one point said that the P2 card had something like 40 commands that it had to issue and respond to. Might have been a tad more difficult of a task than Hoodman was prepared to undertake?

Jim Brennan
04-20-2008, 07:33 AM
That's what I'm thinking. They seem to be a good company, but what they make are largely simple (but effective) mechanical devices. R&D for a P2 card probably costs a ton, and manufacturing tolerances would be pretty tight for a company like that.