On Tue, Feb 11, 2014 at 09:57:40AM -0200, Carlos Maiolino wrote: > > Thanks for clarification, and, this just enforce my concept that ZBC protocol > should be integrated in the generic block layer not make it device-mapper > dependent. So, make this available to any device that supports it with or > without the help of DM. The kernel interface which I have proposed[1] on the linux-fsdevel list is indeed something that would be integrated in the generic block device layer. My hope is that in the near future (I'm waiting for ZBC prototypes to show up in Mountain View ;-) we will have a patches that will allow Linux to recognize ZBC drives, and export the ZBC functionality via the this interface. [1] http://thread.gmane.org/gmane.linux.file-systems/81970/focus=82309 I also hope that in the near-term future we will have at least one device-mapper "SMR simulator" which take a standard block device, and add write-pointer tracking, and then export the same interface. This would allow file systems (perhaps btrfs) to experiment with working with SMR drives, without having to wait for getting a hold of one of the ZBC drives. It would also allow people who are interested in writing a device mapper shim layer which takes a SMR drive, and exports a host-assisted block device. Of course, the stacking of the device mapper layers: HDD <-> SMR_SIMULATOR <-> SMR_ADAPTER is basically a no-op except for introducing performance delays. But the idea here is not performance, but allow people to debug their code. So the use cases: HDD <-> SMR_SIMULATOR <-> SMR_ADAPTER <-> stock linux file system HDD <-> SMR_SIMULATOR <-> SMR_ADAPTER <-> ext4 modified to be SMR-friendly HDD <-> SMR_SIMULATOR <-> modified btrfs that supports ZBC would eventually become: SMR HDD <-> SMR_ADAPTER <-> stock linux file system SMR_HDD <-> SMR_ADAPTER <-> ext4 modified to be SMR-friendly SMR_HDD <-> modified btrfs that supports ZBC And while we wait for SMR_HDD's to become generally available to all kernel developers, the existence of the device-mapper smr simulator will enable us to start work on the device-mapper smr adapter, and file systems that are either modified to be SMR-friendly, or modified to work directly w/o any adapter layers with SMR drives. Regards, - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
