Re: support for sata7 Streaming Feature Set?

From: Lennart Sorensen
Date: Wed May 17 2006 - 09:39:37 EST

On Wed, May 17, 2006 at 11:30:55AM +0300, Jan Wagner wrote:
> Maybe yes, that, or hdparm, but it seems like a horrible hack :) And sg
> being for generic SCSI, I'm not sure how well ATA-7 fits in. At least,
> the current debian sg-tools, and commands like 'sg_opcodes /dev/sda'
> return "Fixed format, current; Sense key: Illegal Request", "Additional
> sense: Invalid command operation code" for those SATA disks I tried.
> Doesn't look good for sg useability, AFAICT.

Just because sgtools doesn't work with it doesn't mean there aren't
commands you can send through sg to work with it.

> To record or play back real-time continuous streamed data that is not
> error-critical but delay critical, from/to a bidirectional data
> aquisition card at ~1Gbit/s over longer time spans.

Do you know of a disk that can handle 1Gbit/s to the platter? Or are
you planning to stripe this across multiple disks?

I would think a controller on a fast enough bus (plain PCI isn't going
to handle it), with enough drives in a raid setup of the right type
should probably handle it. Might need to do a filesystem specially
designed for the streaming needs rather than general purpose file

> Direct kernel device support for the feature set could also be very useful
> for linux projects like the Digital Video Recorder and Video Disk
> Recorder. And seek/stutter free video playback from DVD/ATAPI (scratched
> disks, for example) or video editing. Etc.

Can you tell a DVD drive to stop retrying? Perhaps you can. I know
some of the retries are in software.

Len Sorensen
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