Backups can already be done for multiple drives in a transaction. However, these
jobs will start all at once, potentially hogging a lot of disk IO all at once.
This problem is made worse, since IO throttling is only available on a per-job
basis.
Add a flag to QMP to support sequential transactions for backups. This way,
every job will be executed one after the other, while still providing the
benefit of transactions (i.e. once one fails, all remaining ones will be
cancelled).
We've internally (in Proxmox VE) been doing sequential backups for a long time
with great success, albeit in a different fashion. This series is the result of
aligning our internal changes closer to upstream, and might be useful for other
people as well.
Stefan Reiter (3):
job: add sequential transaction support
blockdev: add sequential mode to *-backup transactions
backup: initialize bcs bitmap on job create, not start
block/backup.c | 4 ++--
blockdev.c | 25 ++++++++++++++++++++++---
include/qemu/job.h | 12 ++++++++++++
job.c | 24 ++++++++++++++++++++++++
qapi/transaction.json | 6 +++++-
5 files changed, 65 insertions(+), 6 deletions(-)