Nir Soffer has posted comments on this change. Change subject: freeze: Freeze guest even when creating memory snapshot ......................................................................
Patch Set 3: (1 comment) https://gerrit.ovirt.org/#/c/43299/3//COMMIT_MSG Commit Message: Line 10: probably done because qemu is pausing the vm for creating memory Line 11: snapshot. Line 12: Line 13: However, this is not consistent with snapshots of external disks such as Line 14: network disks, where we always freeze the vm before taking the snapshot. > why does it need to be consistent? AFAIK we freeze non-memory snapshots for I think we have 2 reason for freezing: - Keep disk state consistent with each other - all io is frozen in same time on all disks. - Keep application state consistent - freezing will run application specific hooks (e.g. /etc/qemu-ga/fsfreeze-hooks.d/myapp-fsfreeze-hook). This gives an application chance to prepare for freezing before filesystems are freezed. Also if an application is writing directly to device (e.g. database) filesystem freezing does not effect the application, but freezing hooks may be used to prepare for snapshot. Depending on pause during memory snapshot does not achive the second goal. And indeed libvirt provide the option to freeze when you do a memory snapshot. See https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Virtualization_Deployment_and_Administration_Guide/sect-QEMU_Guest_Agent-Using_the_QEMU_guest_virtual_machine_agent_protocol_CLI.html#sect-Using_the_QEMU_guest_virtual_machine_agent_protocol_CLI-Creating_a_guest_virtual_machine_disk_backup Line 15: Also, it is probably safer to freeze even when creating memory snapshot, Line 16: giving applications on the guest chance to pause in consistent state. Line 17: Line 18: This patch removes the check for memory snapshot, and freeze the guest -- To view, visit https://gerrit.ovirt.org/43299 To unsubscribe, visit https://gerrit.ovirt.org/settings Gerrit-MessageType: comment Gerrit-Change-Id: I8aa7ac0dea8690ca33df8067f84734d788da8bf8 Gerrit-PatchSet: 3 Gerrit-Project: vdsm Gerrit-Branch: master Gerrit-Owner: Nir Soffer <[email protected]> Gerrit-Reviewer: Adam Litke <[email protected]> Gerrit-Reviewer: Allon Mureinik <[email protected]> Gerrit-Reviewer: Dan Kenigsberg <[email protected]> Gerrit-Reviewer: Federico Simoncelli <[email protected]> Gerrit-Reviewer: Francesco Romani <[email protected]> Gerrit-Reviewer: Jenkins CI Gerrit-Reviewer: Michal Skrivanek <[email protected]> Gerrit-Reviewer: Michal Skrivanek <[email protected]> Gerrit-Reviewer: Nir Soffer <[email protected]> Gerrit-Reviewer: [email protected] Gerrit-HasComments: Yes _______________________________________________ vdsm-patches mailing list [email protected] https://lists.fedorahosted.org/mailman/listinfo/vdsm-patches
