Damien, > Single LUN multi-actuator hard-disks are cappable to seek and execute > multiple commands in parallel. This capability is exposed to the host > using the Concurrent Positioning Ranges VPD page (SCSI) and Log (ATA). > Each positioning range describes the contiguous set of LBAs that an > actuator serves. I have to say that I prefer the multi-LUN model. > The first patch adds the block layer plumbing to expose concurrent > sector ranges of the device through sysfs as a sub-directory of the > device sysfs queue directory. So how do you envision this range reporting should work when putting DM/MD on top of a multi-actuator disk? And even without multi-actuator drives, how would you express concurrent ranges on a DM/MD device sitting on top of a several single-actuator devices? While I appreciate that it is easy to just export what the hardware reports in sysfs, I also think we should consider how filesystems would use that information. And how things would work outside of the simple fs-on-top-of-multi-actuator-drive case. -- Martin K. Petersen Oracle Linux Engineering
