mirror_zfs/lib
Matthew Ahrens fc6700425a Deprecate deduplicated send streams
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 #7887
Closes #10117
2020-05-12 10:53:32 -07:00
..
libavl Support -fsanitize=address with --enable-asan 2018-01-10 10:49:27 -08:00
libefi cppcheck: (error) Memory leak: vtoc 2020-01-22 13:49:06 -08:00
libicp Add support for selecting encryption backend 2018-08-02 11:59:24 -07:00
libnvpair Use correct format string when printing int8 2020-01-22 13:49:03 -08:00
libshare Modify sharenfs=on default behavior 2020-01-22 13:49:03 -08:00
libspl libspl: declare aok extern in header 2020-01-22 13:49:06 -08:00
libtpool Fix typos in lib/ 2020-01-22 13:48:59 -08:00
libunicode Support -fsanitize=address with --enable-asan 2018-01-10 10:49:27 -08:00
libuutil Update build system and packaging 2018-05-29 16:00:33 -07:00
libzfs Deprecate deduplicated send streams 2020-05-12 10:53:32 -07:00
libzfs_core Use ZFS_DEV macro instead of literals 2019-09-25 11:27:48 -07:00
libzpool Implement -A (ignore ASSERTs) for zdb 2020-01-22 13:49:04 -08:00
libzutil Implement ZPOOL_IMPORT_UDEV_TIMEOUT_MS 2020-01-22 13:49:03 -08:00
Makefile.am Add libzutil for libzfs or libzpool consumers 2018-11-05 11:22:33 -08:00