[pve-devel] [PATCH 00/11] live-restore for PBS snapshots

Stefan Reiter s.reiter at proxmox.com
Mon Jan 11 12:13:58 CET 2021

"live-restore" allows starting a VM immediately from a backup snapshot, no
waiting for a long restore process. This is made possible with QEMU backing
images, i.e. data is read from the backup which is attached to the VM as a
drive, but new data is written to the destination, while a background process
('block-stream') copies over data in a linear fashion as well.

QEMU backing images are normally only supported for qcow2 images, but since the
destination always starts out empty, we can use a dirty bitmap to achieve the
same effect - this is implemented as the 'alloc-track' driver in the 'qemu' part
of the series.

The Rust part of the equation is adjusted to provide (quiet a lot) more caching,
as mixing random read/write from the guest with the linear reads from the
background process (both of which may use read sizes smaller or bigger than a
single chunk) would thrash performance without large buffers.

I've marked the feature as 'experimental' in the GUI for now, as I'm sure there
are a lot of edge cases I've missed to test, and there's also the possibility of
data loss, since anything the VM writes during the restore is removed if the
restore fails.

qemu: Stefan Reiter (3):
  PVE: explicitly add libuuid as linking dependency
  PVE: block/pbs: fast-path reads without allocation if possible
  block: add alloc-track driver

 Makefile.objs       |   2 +
 block/Makefile.objs |   1 +
 block/alloc-track.c | 319 ++++++++++++++++++++++++++++++++++++++++++++
 block/pbs.c         |  17 ++-
 4 files changed, 336 insertions(+), 3 deletions(-)
 create mode 100644 block/alloc-track.c

proxmox-backup: Stefan Reiter (1):
  RemoteChunkReader: add LRU cached variant

 src/bin/proxmox_backup_client/mount.rs |  4 +-
 src/client/remote_chunk_reader.rs      | 77 ++++++++++++++++++++------
 2 files changed, 62 insertions(+), 19 deletions(-)

proxmox-backup-qemu: Stefan Reiter (1):
  access: use bigger cache and LRU chunk reader

 src/restore.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

qemu-server: Stefan Reiter (5):
  make qemu_drive_mirror_monitor more generic
  cfg2cmd: allow PBS snapshots as backing files for drives
  enable live-restore for PBS
  extract register_qmeventd_handle to QemuServer.pm
  live-restore: register qmeventd handle

 PVE/API2/Qemu.pm         |  15 ++-
 PVE/QemuServer.pm        | 263 ++++++++++++++++++++++++++++++++-------
 PVE/VZDump/QemuServer.pm |  32 +----
 3 files changed, 233 insertions(+), 77 deletions(-)

manager: Stefan Reiter (1):
  ui: restore: add live-restore checkbox

 www/manager6/grid/BackupView.js    |  8 +++++--
 www/manager6/storage/BackupView.js |  7 ++++--
 www/manager6/window/Restore.js     | 38 +++++++++++++++++++++++++++++-
 3 files changed, 48 insertions(+), 5 deletions(-)


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