diff --git a/en_US.ISO8859-1/books/handbook/zfs/chapter.xml b/en_US.ISO8859-1/books/handbook/zfs/chapter.xml
--- a/en_US.ISO8859-1/books/handbook/zfs/chapter.xml
+++ b/en_US.ISO8859-1/books/handbook/zfs/chapter.xml
@@ -2926,6 +2926,69 @@
However since quotas do not consider compression, more data
may be written than would fit with uncompressed
backups.
+
+
+ Zstandard Compression
+
+ In OpenZFS 2.0, a new compression
+ algorithm was added. Zstandard (Zstd)
+ offers higher compression ratios than the default
+ LZ4 while offering much greater speeds
+ than the alternative, gzip.
+ OpenZFS 2.0 is available starting with
+ &os; 12.1-RELEASE via
+ sysutils/openzfs and is the default in
+ &os; 13.0.
+
+ Zstandard provides a large selection of compression
+ levels, providing fine-grained control over performance
+ versus compression ratio. One of the main advantages of
+ Zstd is that the decompression speed is
+ independent of the compression level. For data that is
+ written once but read many times, there is no disadvantage
+ to using higher compression levels as the read speed will be
+ just as fast as if a lesser compression level had been
+ used.
+
+ Even when data is updated frequently, there are often
+ performance gains that come from enabling compression. One
+ of the biggest advantages comes from the compressed ARC
+ feature. ZFS's Adaptive Replacement
+ Cache (ARC) caches the compressed version
+ of the data in RAM, decompressing it each
+ time it is needed. This allows the same amount of cache to
+ store more data and metadata, increasing the cache hit
+ ratio.
+
+ ZFS offers 19 levels of Zstandard
+ compression, each offering incrementally more space savings
+ in exchange for slower compression. The default level is
+ zstd-3 and offers greater compression
+ than LZ4 without being significantly
+ slower. Levels above 10 require significant amounts of
+ memory to compress each block, so they are discouraged on
+ systems with less than 16 GB of RAM.
+ ZFS also implements a selection of the
+ Zstandard fast levels, which get
+ correspondingly faster but offer lower compression ratios.
+ ZFS supports
+ zstd-fast-1 through
+ zstd-fast-10,
+ zstd-fast-20 through
+ zstd-fast-100 in increments of 10, and
+ finally zstd-fast-500 and
+ zstd-fast-1000 which provide minimal
+ compression, but offer very high performance.
+
+ If ZFS is not able to allocate the required memory to
+ compress a block with Zstandard, it will fall back to
+ storing the block uncompressed. This is unlikely to happen
+ outside of the highest levels of Zstandard on systems that
+ are memory constrained. The sysctl
+ kstat.zfs.misc.zstd.compress_alloc_fail
+ counts how many times this has occurred since the
+ ZFS module was loaded.
+