'zfs send -i': destination has been modified

[Ruben de Groot]

On Wed, Oct 20, 2010 at 08:32:33AM -0400, Dan Langille typed:
> I am trying to do a 'zfs send -i' and failing.
> 
> This is my simple proof of concept test:
> 
> Create the data
> # zfs create storage/a
> # touch /storage/a/1
> # touch /storage/a/2
> # touch /storage/a/3
> 
> Snapshot
> # zfs snapshot storage/a at 2010.10.19
> 
> send
> # zfs send storage/a at 2010.10.19 | zfs receive -v storage/compressed/a
> receiving full stream of storage/a at 2010.10.19 into
> storage/compressed/a at 2010.10.19
> received 252KB stream in 2 seconds (126KB/sec)
> #
> 
> 
> 
> Create one more file and snapshot that
> 
> # touch /storage/a/4
> # zfs snapshot storage/a at 2010.10.20
> 
> 
> send it
> 
> # zfs send -i storage/a at 2010.10.19  storage/a at 2010.10.20 | zfs receive -v
> storage/compressed/a
> receiving incremental stream of storage/a at 2010.10.20 into
> storage/compressed/a at 2010.10.20
> received 250KB stream in 3 seconds (83.4KB/sec)
> 
> What do we have?
> 
> # find /storage/compressed/a
> /storage/compressed/a
> /storage/compressed/a/1
> /storage/compressed/a/2
> /storage/compressed/a/3
> /storage/compressed/a/4
> 
> 
> Of note:
> 
> * FreeBSD 8.1-STABLE
> * ZFS filesystem version 4.
> * ZFS pool version 15.
> * zfs send is on compression off
> * zfs receive has compression on
> 
> What I actually want to do and what fails:
> 
> 
> # zfs snapshot storage/bacula at 2010.10.19
> 
> # zfs send storage/bacula at 2010.10.19 | zfs receive -v
> storage/compressed/bacula
> receiving full stream of storage/bacula at 2010.10.19 into
> storage/compressed/bacula at 2010.10.19
> received 4.38TB stream in 42490 seconds (108MB/sec)
> 
> # zfs snapshot storage/bacula at 2010.10.20
> 
> # zfs send -i storage/bacula at 2010.10.19 storage/bacula at 2010.10.20 | zfs
> receive -v storage/compressed/bacula
> receiving incremental stream of storage/bacula at 2010.10.20 into
> storage/compressed/bacula at 2010.10.20
> cannot receive incremental stream: destination storage/compressed/bacula
> has been modified
> since most recent snapshot
> warning: cannot send 'storage/bacula at 2010.10.20': Broken pipe
> 
> I have no idea why this fails.  Clues please?
> 
> To my knowledge, the destination has not been written to.

Has any read operation been done on the destination (ie: updated atime) ?

Ruben