On Thu, 2013-02-21 at 23:05 +0100, Ric Wheeler wrote: > On 02/21/2013 09:00 PM, Paolo Bonzini wrote: > > Il 21/02/2013 15:57, Ric Wheeler ha scritto: > >>> sendfile64() pretty much already has the right arguments for a > >>> "copyfile", however it would be nice to add a 'flags' parameter: the > >>> NFSv4.2 version would use that to specify whether or not to copy file > >>> metadata. > >> That would seem to be enough to me and has the advantage that it is an > >> relatively obvious extension to something that is at least not totally > >> unknown to developers. > >> > >> Do we need more than that for non-NFS paths I wonder? What does reflink > >> need or the SCSI mechanism? > > For virt we would like to be able to specify arbitrary block ranges. > > Copying an entire file helps some copy operations like storage > > migration. However, it is not enough to convert the guest's offloaded > > copies to host-side offloaded copies. > > > > Paolo > > I don't think that the NFS protocol allows arbitrary ranges, but the SCSI > commands are ranged based. > > If I remember what the windows people said at a SNIA event a few years back, > they have a requirement that the target file be pre-allocated (at least for the > SCSI based copy). Not clear to me where they iterate over that target file to do > the block range copies, but I suspect it is in their kernel. The NFSv4.2 copy offload protocol _does_ allow the copying of arbitrary byte ranges. The main target for that functionality is indeed virtualisation and thin provisioning of virtual machines. -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust@xxxxxxxxxx www.netapp.com -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
