Re: Expected Received UUID

[Cerem Cem ASLAN <ceremcem@xxxxxxxxxxxx>]

Not an answer, but exactly same case: https://unix.stackexchange.com/questions/377914/how-to-test-if-two-btrfs-snapshots-are-identical

2018-07-31 20:42 GMT+03:00 Gaurav Sanghavi <gaurav.ms5@xxxxxxxxx>:

Hello everyone, 

While researching BTRFS for a project that involves backing up snapshots from device A to device B 

before consolidating backups from device B to device C, I noticed that received UUID on snapshot on 

device C is not the same as received UUID for the same snapshot on device B. Here are my steps:

1. Device A

BTRFS version: v3.17

btrfs su sn -r /home/test/snapshot1 /home/test/snaps/snapshot1

btrfs su show /home/test/snaps/snapshot1

Name: snapshot1

uuid: b00e8ba1-5aaa-3641-9c4c-e168eee5c296

Parent uuid: cb570dec-e9fd-1f40-99d2-2070c8ee2466

        Received UUID:      ---

Creation time: 2018-07-30 18:32:37

Flags: readonly

2. Send to Device B

btrfs send /home/test/snaps/snapshot1 | ssh <device b> 'btrfs receive /home/backups/'

After send completes, on Device B

BTRFS version: v4.7.3

btrfs su show /home/backups/snapshot1

Name: snapshot1

UUID: 7c13d189-7fee-584e-ac90-e68cb0012f5c

Parent UUID: a2314f7c-4b11-ed40-901f-f1acb5ebf802

Received UUID: b00e8ba1-5aaa-3641-9c4c-e168eee5c296

Creation time: 2018-07-30 18:42:37 -0700

Flags: readonly

3. Send to Device C

btrfs send /home/backups/snapshot1 | ssh <device c> 'btrfs receive /home/backups2/'

After send completes, on Device C

BTRFS version: v4.7.3

btrfs su show /home/backups2/snapshot1

Name: snapshot1

UUID: 8a13aab5-8e44-2541-9082-bc583933b964

Parent UUID: 54e9b4ff-46dc-534e-b70f-69eb7bb21028

Received UUID: 7c13d189-7fee-584e-ac90-e68cb0012f5c

Creation time: 2018-07-30 18:58:32 -0700

Flags: readonly

1. I have gone through some of the archived emails and have noticed people mentioning that

if received UUID is set, btrfs send propogates this 'received UUID'. But in above case, 

it's different for the same snapshot on all three devices. Is this the expected behavior ?

2. We want to be able to start backing up from Device A to C, in case B goes down or needs 

to be replaced. If received UUID is expected to differ for the snapshot on device B and C, incremental

backups will not work from A to C without setting received UUID. I have seen python-btrfs

mentioned in a couple of emails; but have anyone of you used it in a production environment ?

This is my first post to this email. Please let me know if I am missing any details.

Thanks,

Gaurav