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Hi, On Wed, 17 May 2006, Lennart Sorensen wrote: > > 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 > storage. Yes, multiple disks striped in RAID-0, 4 x DiamondMax 10 300GB, ext2 fs. On a cheapish Dell OptiPlex GX620 that uses Intel 945G. 1.6Gbit/s write to disk while reading PCI(-X) goes just fine, though of course gets slower near disk ends. Streaming filesystems, yes, that's what I'd like to evaluate next vs ext2 once the Samsung SP2504C disks with Streaming Feature Set support arrive. > > 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. Ok, probably yes, this is also something to be done outside of kernel. However this guy over here http://www.ussg.iu.edu/hypermail/linux/kernel/0411.3/0338.html has written speedcontrol.c for SET STREAMING (linked pdf there, page 457), which is somewhat similar to the commands in the Streaming feature set. One quote: "In my opinion it would make sence to also enhance the kernel function cdrom_select_speed (linux/drivers/ide/ide-cd.c), so that this function works also for "newer" DVD-drives." etc But OTOH also Tejun's points about that this Streaming set should be implemented in userland are quite valid. And I don't know where exactly such functionality could be added to the kernel i.e. where I would propose such a feature to be added; it was a thought there might be some suitable place and people here would know where to add ;-)) But actually after googling more, XFS file system seems to have something like Streaming feature set support, or at least provisions for adding such commands, as it has a guaranteed-rate I/O feature http://en.wikipedia.org/wiki/XFS#Guaranteed_rate_I.2FO So I guess XFS code is the better place to start thinking about Streaming feature set implementation. Many thanks for your input! :-)) - Jan - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||
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