Dedup send can only deduplicate over the set of blocks in the send
command being invoked, and it does not take advantage of the dedup table
to do so. This is a very common misconception among not only users, but
developers, and makes the feature seem more useful than it is. As a
result, many users are using the feature but not getting any benefit
from it.
Dedup send requires a nontrivial expenditure of memory and CPU to
operate, especially if the dataset(s) being sent is (are) not already
using a dedup-strength checksum.
Dedup send adds developer burden. It expands the test matrix when
developing new features, causing bugs in released code, and delaying
development efforts by forcing more testing to be done.
As a result, we are deprecating the use of `zfs send -D` and receiving
of such streams. This change adds a warning to the man page, and also
prints the warning whenever dedup send or receive are used.
In a future release, we plan to:
1. remove the kernel code for generating deduplicated streams
2. make `zfs send -D` generate regular, non-deduplicated streams
3. remove the kernel code for receiving deduplicated streams
4. make `zfs receive` of deduplicated streams process them in userland
to "re-duplicate" them, so that they can still be received.
Reviewed-by: Paul Dagnelie <pcd@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes#7887Closes#10117
Currently when the dataset is in use we can't receive snapshots.
zfs send test/1@asd | zfs recv -FM test/2
cannot unmount '/test/2': Device busy
This commits add option 'M' which attempts to forcibly unmount the
dataset. Thanks to this we can enforce receiving snapshots in a
single step.
Note that this functionality is not supported on Linux because the
VFS will prevent active mounted filesystems from being unmounted,
even with the force option. This is the intended VFS behavior.
Test cases were added to verify the expected behavior based on
the platform.
Discussed-with: Pawel Jakub Dawidek <pjd@FreeBSD.org>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Allan Jude <allanjude@freebsd.org>
External-issue: https://reviews.freebsd.org/D22306Closes#9904
Most subcommands got their own manpages (e.g. create). Some related
commands grouped into a single manpage and symlinks created (e.g. set,
get, and inherit). I did this when topics were either too short to
warrant their own file or so interrelated that a user would want to
refer between commands in the same file.
Corrected .Sx internal references to .Xr cross refs; lots of .Sx
references from when text was all in zfs.8 needed to be changed to
.Xr zfs-$SUBCOMMAND 8 cross references.
Divided subcommand list in zfs(8) into sections of related
functionality. This required writing new descriptions for some
commands.
Preserved ".Os Linux", `.Os` macro parsing behavior differs between
mandoc from the "BSD" mandoc package (available on Ubuntu) and man
from Ubuntu's man-db package, which calls groff to format the manpages.
Groff handles the `.Os` macro differently and wrongly, defaulting
it to "BSD" in `/usr/share/groff/*/tmac/mdoc/doc-common`, instead of
getting the default from `uname`.
A future set of changes will introduce build-time preprocessing of
manpages for platform-specific documentation and can insert the
correct operating system name.
Added SEE ALSO sections, the newly-divided zfs-*.8 subcommand man
pages needed their own SEE ALSO sections pointing to related
subcommands and, in some cases, documentation from other packages
(e.g. zfs-share.8).
Reviewed-by: Matt Ahrens <matt@delphix.com>
Reviewed-by: Kjeld Schouten <kjeld@schouten-lebbing.nl>
Reviewed-by: Sean Eric Fagan <sef@ixsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ross Williams <ross@ross-williams.net>
Closes#9559
Matthew Ahrens
Mariusz Zaborski
Ross Williams