Re: btrfs send reproducibly fails for a specific subvolume after sending 15 GiB, scrub reports no errors

[Christoph Anton Mitterer <calestyo@scientia.net>]

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On Tue, 2015-11-24 at 15:58 -0500, Austin S Hemmelgarn wrote:
> I had tried using send/receive once with -p, but had numerous issues.
 
> The incrementals I've been doing have used -c instead, and I hadn't had 
> any issues with data loss with that.  The issue outlined here was only a 
> small part of why I stopped using it for backups.  The main reason was 
> to provide better consistency between my local copies and what I upload 
> to S3/Dropbox, meaning I only have to test one back up image per 
> filesystem backed-up, instead of two.

Okay maybe I just don't understand how to use send/receive correctly...


What I have is about the following (simplified):

master-fs:
5
|
+--data (subvol, my precious data)
|
+--snapshots
   |
   +--2015-11-01 (suvol, ro-snapshot of /data)

So 2015-11-01 is basically the first snapshot ever made.

Now I want to have it on:
backup-fs
+--2015-11-01 (suvol, ro-snapshot of /data)


So far I did
btrfs send /master-fs/snapshots/2015-11-01 | btrfs receive /backup-fs/2015-11-01




Then time goes by and I get new content in the data subvol, so what
I'd like to have then is a new snapshot on the master-fs:
5
|
+--data (subvol, more of my precious data)
|
+--snapshots
   |
   +--2015-11-01 (suvol, ro-snapshot of /data)
   +--2015-11-20 (suvol, ro-snapshot of /data)

And this should go incrementally on backup-fs:
backup-fs
+--2015-11-01 (suvol, ro-snapshot of /data)
+--2015-11-20
(suvol, ro-snapshot of /data)

So far I used something like:
btrfs send -p 2015-11-01 /master-fs/snapshots/2015-11-20 | btrfs receive /backup-fs/2015-11-20

And obviously I want it to share all the ref-links and stuf...


So in other words, what's the difference between -p and -c? :D


Thx,
Chris.

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