> On Aug 12, 2016, at 7:17 AM, Ilya Dryomov <idryomov@xxxxxxxxx> wrote: > > On Fri, Aug 12, 2016 at 1:38 AM, Kamble, Nitin A > <Nitin.Kamble@xxxxxxxxxxxx> wrote: >> >> SCSI block devices has SG_IO IOCTL interface by which applications can identify the device uniquely. This helps applications identify the device uniquely without relying on the device file names or any other mechanisms. >> >> For more details l ook at the manpage of sg_inq commnad. https://manned.org/sg_inq >> >> Some of the non SCSI devices also support this SG_IO interface for inquiry. Examples include SATA, NVME, Virtual Disks. >> >> It is desired to identify every RBD uniquely just from the device file. It will help in using RBD devices as drop in replacement for SCSI/SATA devices. Currently the RBD code in ceph-client does not support the SG_IO ioctl interface for inquiry to identify the device uniquely. Has adding the SG_IO ioctl interface to the RBD devices ever been considered before? > > No, SG_IO hasn't come up before, and we don't really have a good > established way of doing that at all - if we had one, wiring up SG_IO > (assuming no objections from SCSI maintainers) wouldn't be a problem. > One approach is to concatenate a cluster-wide UUID with pool, image and > snapshot IDs, but the problem there is that images can be moved between > pools and clusters and v1 images don't have an image ID. I am surprised to know that images can be moved across pools and clusters. The feature request for moving images across pools was rejected here: http://tracker.ceph.com/issues/2305 . Also the rbd man page says rbd rename across pools is not supported. (http://docs.ceph.com/docs/master/man/8/rbd/) Is it a currently available feature? > > Mike recently ran into the need to uniquely identify RBD devices for > his multipath-tools work and I think he ended up using some variant of > the above approach, grabbing IDs from /sys/bus/rbd. (The cluster_uuid > and snap_id attributes currently don't exist, but will be added in the > next kernel release.) > > It would make this a lot easier if we started generating a unique UUID > for the image and each snapshot at image/snapshot creation time. Jason? > Image UUID seems like the right direction. If that UUID needs to be really unique, then image copy also need to create a new UUID. Thanks, Nitin > Thanks, > > Ilya -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
