On 27/09/2016 15:28, Denis V. Lunev wrote: > On 09/27/2016 03:07 PM, Paolo Bonzini wrote: >> >> ----- Original Message ----- >>> From: "Denis V. Lunev" <d...@virtuozzo.com> >>> To: "Paolo Bonzini" <pbonz...@redhat.com> >>> Cc: "Vladimir Sementsov-Ogievskiy" <vsement...@virtuozzo.com>, >>> qemu-de...@nongnu.org, qemu-block@nongnu.org, >>> nbd-gene...@lists.sourceforge.net, a...@alex.org.uk, ebl...@redhat.com, >>> kw...@redhat.com, stefa...@redhat.com, >>> w...@uter.be >>> Sent: Tuesday, September 27, 2016 12:25:54 PM >>> Subject: Re: [PATCH] proto: add 'shift' extension. >>> >>> On 09/27/2016 01:15 PM, Paolo Bonzini wrote: >>>>> We could go in a different direction and export flag >>>>> 'has_zero_init' which will report that the storage is >>>>> initialized with all zeroes at the moment. In this >>>>> case mirroring code will not fall into this >>>>> branch. >>>> Why don't you add the zero_init flag to QEMU's NBD driver instead? >>> for all cases without knowing real backend on the server side? >>> I think this would be wrong. >> Add it to the command line, and leave it to libvirt or the user to >> pass "-drive file.driver=nbd,...,file.zero-init=on". > > I have started with something very similar for 'drive-mirror' command. > We have added additional flag for this to improve migration speed > and this was rejected.
You can add it through the filename path too, through a URI option "nbd://...?zero-init=on". Paolo
