[libvirt-users] Why librbd disallow VM live migration if the disk cache mode is not none or directsync
I'm curious that why librbd sets this limitation? The rule first appeared in librbd.git commit d57485f73ab. Theoretically, a write-through cache is also safe for VM migration, if the cache implementation guarantees that cache invalidation and disk write are synchronous operations. For example, I'm using Ceph RBD images as VM storage backend. The Ceph librbd supports synchronous write-through cache, by setting rbd_cache_max_dirty to zero, and setting rbd_cache_block_writes_upfront to true, thus it would be safe for VM migration. Is that true? Any suggestion would be appreciated. Thanks. Ming-Hung Tsai ___ libvirt-users mailing list libvirt-users@redhat.com https://www.redhat.com/mailman/listinfo/libvirt-users
Re: [libvirt-users] Why librbd disallow VM live migration if the disk cache mode is not none or directsync
Sorry, the title and content are wrong. I mean libvirt, not librbd. Ming-Hung Tsai : > > I'm curious that why librbd sets this limitation? The rule first > appeared in librbd.git commit d57485f73ab. Theoretically, a > write-through cache is also safe for VM migration, if the cache > implementation guarantees that cache invalidation and disk write are > synchronous operations. > > For example, I'm using Ceph RBD images as VM storage backend. The Ceph > librbd supports synchronous write-through cache, by setting > rbd_cache_max_dirty to zero, and setting > rbd_cache_block_writes_upfront to true, thus it would be safe for VM > migration. Is that true? Any suggestion would be appreciated. Thanks. ___ libvirt-users mailing list libvirt-users@redhat.com https://www.redhat.com/mailman/listinfo/libvirt-users
Re: [libvirt-users] OVS / KVM / libvirt / MTU
On 7/23/19 8:00 PM, Sven Vogel wrote: Hey there, I hope anyone can bring some light in the following problem. we have an base bridge for example and cloudbr0. After we add an mtu to the vm bridge here it seems the base bridge gets the same mtu like the vnet adapter. Is this normal behaviour of libvirt together with OVS? I wouldn't say it is 'normal', but this behaviour is not specific to libvirt. I mean, if you create a tap device yourself by hand and then plug it into an ovs bridge the same thing will happen. If you don't want to change MTU of the bridge then just don't set it for and libvirt will copy whatever MTU the bridge has over to the new TAP device. Michal ___ libvirt-users mailing list libvirt-users@redhat.com https://www.redhat.com/mailman/listinfo/libvirt-users
Re: [libvirt-users] Why librbd disallow VM live migration if the disk cache mode is not none or directsync
On 7/29/19 3:51 AM, Ming-Hung Tsai wrote: I'm curious that why librbd sets this limitation? The rule first appeared in librbd.git commit d57485f73ab. Theoretically, a write-through cache is also safe for VM migration, if the cache implementation guarantees that cache invalidation and disk write are synchronous operations. For example, I'm using Ceph RBD images as VM storage backend. The Ceph librbd supports synchronous write-through cache, by setting rbd_cache_max_dirty to zero, and setting rbd_cache_block_writes_upfront to true, thus it would be safe for VM migration. Is that true? Any suggestion would be appreciated. Thanks. The commit you refer to is very old and my hunch is that things looked different in 2012. Things might have changed since then and if write-through wasn't safe ~7 years ago, it might be safe now (with some tuning). Michal ___ libvirt-users mailing list libvirt-users@redhat.com https://www.redhat.com/mailman/listinfo/libvirt-users
[libvirt-users] virsh command to list CPU,Memory and Storage
Hi, Is there a way to find out total CPU's, Memory and Storage using virsh command? For example virsh list --all list out all VM's 11dockerregistry01 running 12gitlab running Any help will be highly appreciated. Thanks in Advance. Best Regards, Kaushal ___ libvirt-users mailing list libvirt-users@redhat.com https://www.redhat.com/mailman/listinfo/libvirt-users
Re: [libvirt-users] OVS / KVM / libvirt / MTU
Hi Michal, Thanks for your answer. I don’t understand why an interface created without mtu gets only 1500 visible in the virtual machine but if I create an interface with mtu higher than 1500 e.g. 2000 the bridge will change too. Before the bridge was e.g. by 9000. I ask because you wrote if I don’t set an mtu of the interface I will get the mtu of the bridge. But it seems so. Can you clarify it a little better for me? Cheers Sven Von meinem iPhone gesendet __ Sven Vogel Teamlead Platform EWERK RZ GmbH Brühl 24, D-04109 Leipzig P +49 341 42649 - 11 F +49 341 42649 - 18 s.vo...@ewerk.com www.ewerk.com Geschäftsführer: Dr. Erik Wende, Hendrik Schubert, Frank Richter Registergericht: Leipzig HRB 17023 Zertifiziert nach: ISO/IEC 27001:2013 DIN EN ISO 9001:2015 DIN ISO/IEC 2-1:2011 EWERK-Blog | LinkedIn | Xing | Twitter | Facebook Auskünfte und Angebote per Mail sind freibleibend und unverbindlich. Disclaimer Privacy: Der Inhalt dieser E-Mail (einschließlich etwaiger beigefügter Dateien) ist vertraulich und nur für den Empfänger bestimmt. Sollten Sie nicht der bestimmungsgemäße Empfänger sein, ist Ihnen jegliche Offenlegung, Vervielfältigung, Weitergabe oder Nutzung des Inhalts untersagt. Bitte informieren Sie in diesem Fall unverzüglich den Absender und löschen Sie die E-Mail (einschließlich etwaiger beigefügter Dateien) von Ihrem System. Vielen Dank. The contents of this e-mail (including any attachments) are confidential and may be legally privileged. If you are not the intended recipient of this e-mail, any disclosure, copying, distribution or use of its contents is strictly prohibited, and you should please notify the sender immediately and then delete it (including any attachments) from your system. Thank you. > Am 29.07.2019 um 13:20 schrieb Michal Privoznik : > >> On 7/23/19 8:00 PM, Sven Vogel wrote: >> Hey there, >> I hope anyone can bring some light in the following problem. >> >> >> >> >> >> >> >> >> >> >> >> we have an base bridge for example and cloudbr0. After we add an mtu to the >> vm bridge here it seems the base bridge gets the same mtu like the vnet >> adapter. >> Is this normal behaviour of libvirt together with OVS? > > I wouldn't say it is 'normal', but this behaviour is not specific to libvirt. > I mean, if you create a tap device yourself by hand and then plug it into an > ovs bridge the same thing will happen. If you don't want to change MTU of the > bridge then just don't set it for and libvirt will copy whatever > MTU the bridge has over to the new TAP device. > > Michal ___ libvirt-users mailing list libvirt-users@redhat.com https://www.redhat.com/mailman/listinfo/libvirt-users
