On 11/02/2016 03:49 PM, Hans van Kranenburg wrote: > On 11/02/2016 03:23 PM, René Bühlmann wrote: >> I have a system running on btrfs which is backed up to two (one local >> USB and one through SSH) external drives (also using btrfs) using >> send/receive (with the help of btrbk). For each backup a snapshot is >> created and transferred to the external drives. After some time, the >> snapshot on the origin is removed but kept on the two backups. >> >> Now my problem is, that the SSH-drive has not received any snapshots for >> some time such that there is no snapshot any more which is on the origin >> AND the SSH-drive. I would like to prevent transferring a full snapshot >> over the network and am now trying to work around it. >> >> Here the current situation (S? for a Snapshot): >> >> Origin: S2 S3 >> >> USB: S1 S2 >> >> SSH: S1 >> >> Transferring S3 to USB is no problem as S2 is on both btrfs drives. But >> how can I transfer S3 to SSH? > Since there is no snapshot left that is present on both drives, you > cannot use incremental send. > > btrbk does not remember what snapshots were last transferred or were > present on the missing disk, since the tool does not do any extra meta > administation on top of just having the snapshots on btrfs level. So > it's figuring out the relationships between each of them (combining it > with info from the remotes) again every time it runs. Yes this explains why 1. did not work. But why can't I transfer S1 from USB back to Origin as incremental to S2? And why can't I transfer S2 from USB to SSH? Is S1 not recognized as the same snapshot there? > >> I tried to transfer... >> >> 1. S3 from Origin to SSH -> does not work as there is no common snapshot. >> >> 2. S2 from USB to SSH -> did not work. >> >> 3. S1 from USB to Origin (such that there is a common snapshot with SSH) >> -> did not work. >> >> Is it correct that 1. would work if a common snapshot is present on >> Origin and SSH? >> >> Is it expected that 2. and 3. do not work? >> >> Is there some other way to achieve it? > At home, I do a similar thing, I periodically send/receive changes of a > filesystem to two external disks, also using btrbk. Since I don't want > to have both backup disks and the originating filesystem all online and > in the same geographical location at the same moment, I have the same > problem. > > What I did is just setting expiry the snapshots on the origin manually, > and keep the meta-administration in my head. I don't do it that often > anyway. > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
