On Thu, Feb 13, 2014 at 08:02:43PM +0100, Kai Krakow wrote: > Hi! > > Is it technically possible to wait for a snapshot completely purged from > disk? I imagine an option like "--wait" for btrfs delete subvolume.
I'm sure there's been some patches for that around here somewhere, some time ago. I guess they didn't get merged. Hugo. > This would fit some purposes I'm planning to implement: > > * In a backup scenario have a subprocess which deletes snapshots one by one, > starting with the oldest. If free space raises above a certain threshold, > pause the subprocess. If number of kept snapshots falls below a certain > threshold, exit the subprocess. When the backup job finished, it joins the > subprocess to wait for a pending subvolume deletion if any, then syncs the > filesystem and waits some grace time for uncommitted writes, then shuts > the system down or hibernates it. > > * Wait for pending background subvolume deletion before putting the system > to sleep. > > * Get better control of cron jobs working with subvolumes so jobs either do > not overlap or do not put too much parallel work on the file system. > > Scrubbing does allow that. Why don't snapshots do? At least I found no > options for it. > > Background information: If btrfs is shut down improperly, already deleted > subvolume entries may reappear in their directories. The deletion is not > gracefully resumed. Since deletion of subvolumes/snapshots can take hours, > this is a problem for systems that are not guaranteed to be up all the time > or suffer from disconnected power, especially if multiple snapshots are > being deleted at once. With an option to wait, a script managing snapshot > deletion could more gracefully resume its job. > -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 65E74AC0 from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- Gentlemen! You can't fight here! This is the War Room! ---
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