DV edit on 2nd external HDD

[clms]

Is it possible to edit DV(avi) on 2nd external HDD wit faster RPM than laptop PC?
Regards,
clms

[dipstick]

Yes.

I've done it before with no problems, I'm guessing it's a little slower for the data to travel back and forth through the Firewire or USB 2.0 than it would be through the IDE.

[clms]

Thanks.
Will it faster than on laptop?
I assume I use 7200rpm external HDD vs 5400rpm HDD on my laptop.

Regards,

clms

[dipstick]

The HDD is faster, but the bottle neck lies in the Firewire or USB 2.0 connection. They are surely slower than a direct IDE conection.

For the record, Firewire is faster than USB 2.0. Don't believe what they tell you about the transfer rates, I tested both and can confirm Firewire is faster.

[wayne421]

You can usually edit files on an external harddrive, yes. (I've done it myself on more than one occasion with Premiere).

However, I'm not sure how much speed you will gain... even though you're using a faster RPM drive, you are limited by the USB/Firewire bandwidth. The internal harddrive has a much faster connection since the controller is built into the system.

-W-

[MpegEncoder]

Does anyone have any real data for this? I read lots of opinions, but I'm not seeing any hard numbers.

For example, IDE ATA66 is 66 MB/s and USB 2.0 is 60 MB/s. So from that you don't see much difference. I don't think that the drive itself can keep up with either one of those.

Does anyone really know?

[redwudz]

Not too scientific, but here's what I got with SiSandra and my external 80Gb 2.5" 5400Rpm drive. It has USB 2.0 and Firewire 400 interfaces:

Firewire external 29MB/s
USB 2.0 external 12MB/s

SATA internal 80Gb 47MB/s

I used this freeware version of the SiSandra benchmarking program:

http://www.overclockersclub.com/downloadcenter/?action=file&id=56

[edDV]

Is it possible to edit DV(avi) on 2nd external HDD wit faster RPM than laptop PC?
Regards,
clms

Yes you can edit and encode data that resides on an external drive with no problems but you are better off capturing or transferring to the internal drive because of greater potential for data dropouts or field loss while streaming to an external drive.

Will it faster than on laptop?
I assume I use 7200rpm external HDD vs 5400rpm HDD on my laptop.

Regards,
clms

Will what be faster?

DV video transfers at 25-34 Mb/s (~4MB/sec). Even 4200 RPM internal laptop drives can handle that rate fine. They typically can handle >12 MB/s sustained. Desktop drives handle ~20-50+MB/s sustained.

As said above, external drives are limited buy the interface path. The more hardware and software in the path, the more likely a data drop. During camcorder capture-transfer there is no data error correction. After the data stream is captured into a file on the HDD, the OS takes over and will ensure data is resent until a file is complete and correct.

Path to internal drive:
Camcorder> IEEE-1394> IEEE-1394 adapter> PCI Bus> Memory (influenced by CPU) > PCI Bus > HDD controller > HDD

Path to external drive:
Camcorder> IEEE-1394> IEEE-1394 adapter> PCI Bus> Memory (influenced by CPU) > Software HDD controller (CPU) > Memory > PCI Bus > USB2/IEEE-1394 adapter > USB2/IEEE-1394 transfer > USB2/IEEE-1394 adapter > EIDE HDD adapter > HDD

The long processing path to the external drive makes the probability of camcorder data stream transfer drop more likely.

Bottom line: Capture-transfer to the internal drive. After that you can transfer the DV file to the external drive and use with safety.


PS: I just ran a sustained transfer test to a Western Digital USB2 7200 RPM external drive. It tested at 17 MB/s. The same drive mounted internally scored 43MB/s. Either will work fine for DV file transfer.

[junkmalle]

I just wanted to point out that sustained throughput rates don't tell the entire story when it comes to realtime processes like video capture. Consider this hypothetical scenario:

An external storage device can save data at 34 MB/s for half a second, then completely locks up the computer for half a second. Overall it has an average data throughput of 17 MB/s. But video capture can't be paused for those half seconds the computer is locked up. New frames keep arriving every 1/30 of a second. During the half second lockups 15 frames will be dropped!

Obviously, this is an extreme, unrealistic example. But USB transfers incur much more CPU overhead within a high priority device driver (I see around 35 percent CPU usage copying a file to an external USB2 drive) and many short term delays which could cause frame drops.

I don't have any direct experience capturing DV to an external USB2 drive but just because the sustained throughput is sufficient doesn't mean that frames won't be lost.

[edDV]

Agreed

It is a weakest link in the chain senario. On sufficiently fast computers, CPU process priority determines whether the streaming video is passed or dropped.

A desktop with two or more internal drives (and disk controllers) reduces the problem by isolating capture-transfer from general CPU activity. The OS gets a drive, capture is done directly from the IEEE-1394 port to a separate disk controller through assigned memory. PCI bus mastering keeps the OS and video capture activity separate.

Single drive systems mix the two activities. Frame drops happen when two processes want to take over the CPU activity and/or HDD write at the same time. Most of the time a single drive computer can keep up with all processes, but video transfer requires reliability over the 62min of DV stream transfer.

[dipstick]

I've recorded with Dv-Cam directly to an external HDD via my Laptop through the USB 2.0 and had no frames dropped.

I've also done Tape transfers to External HDD the same way with no dropped frames.

I've also edited said video with Premiere on External HDD via Firewire and encoded to Mpeg. Although I didn't have any problems, it did seem a little slower than if I did it on Internal HDD.

I do have a decent Laptop with an AMD 64 3200+, so your results may vary.

[edDV]

These are mostly problems of the past but clms has a 1.3 GHz laptop. Risk goes up for older and slower equiment or where the CPU is loaded with many background tasks.

[clms]

Thank you to all of your respond.
My intention is to edit the video on my external HDD. So it could faster vs my internal HDD
For sure I would capture via IEEE Port.
Thnaks again.
Regards,

clms

[edDV]

A "faster" drive will only affect file copy, not speed of editing or encoding. Your encoding speed is determined by your 1.3 GHz processor. If you don't need the drive space, save your money.

[junkmalle]

Some Firewire/USB drive comparisons:

http://www.tomshardware.com/storage/20040402/firewire800-06.html