>>>>> "Jens" == Jens Axboe <axboe@xxxxxx> writes: Jens, >> OK. I'm still of the opinion that we should try to make this >> transparent. I could be swayed by workload descriptions and numbers >> comparing approaches, though. Jens> You can't just waive that flag and not have a solution. Any Jens> solution in that space would imply having policy in the kernel. A Jens> "just use a stream per file" is never going to work. I totally understand the desire to have explicit, long-lived "from-file-open to file-close" streams for things like database journals and whatnot. However, I think that you are dismissing the benefits of being able to group I/Os to disjoint LBA ranges within a brief period of time as belonging to a single file. It's something that we know works well on other types of storage. And it's also a much better heuristic for data placement on SSDs than just picking the next available bucket. It does require some pipelining on the drive but they will need some front end logic to handle the proposed stream ID separation in any case. Also, in our experiments we essentially got the explicit stream ID for free by virtue of the journal being written often enough that it was rarely if ever evicted as an active stream by the device. With no changes whatsoever to any application. My gripe with the current stuff is the same as before: The protocol is squarely aimed at papering over issues with current flash technology. It kinda-sorta works for other types of devices but it is very limiting. I appreciate that it is a great fit for the "handful of apps sharing a COTS NVMe drive on a cloud server" use case. But I think it is horrible for NVMe over Fabrics and pretty much everything else. That wouldn't be a big deal if the traditional storage models were going away. But I don't think they are... -- Martin K. Petersen Oracle Linux Engineering -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
