Add zpool properties for allocation class space

The existing zpool properties accounting pool space (size, allocated,
fragmentation, expandsize, free, capacity) are based on the normal
metaslab class or are cumulative properties of several classes combined.

Add properties reporting the space accounting metrics for each metaslab
class individually.

Also introduce pool-wide AVAIL, USABLE, and USED properties reporting
values corresponding to FREE, SIZE, and ALLOC deflated for raidz.

Update ZTS to recognize the new properties and validate reported values.

While in zpool_get_parsable.cfg, add "fragmentation" to the list of
parsable properties.

Sponsored-by: Klara, Inc.
Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ameer Hamza <ahamza@ixsystems.com>
Signed-off-by: Ryan Moeller <ryan.moeller@klarasystems.com>
Cloes #18238

man/man7/zpoolprops.7

@@ -27,9 +27,9 @@
 .\" Copyright 2017 Nexenta Systems, Inc.
 .\" Copyright (c) 2017 Open-E, Inc. All Rights Reserved.
 .\" Copyright (c) 2021, Colm Buckley <colm@tuatha.org>
-.\" Copyright (c) 2023, Klara Inc.
+.\" Copyright (c) 2023, 2026, Klara Inc.
 .\"
-.Dd December 4, 2024
+.Dd March 2, 2026
 .Dt ZPOOLPROPS 7
 .Os
 .
@@ -49,7 +49,7 @@ For more information about user properties, see the
 section.
 .Pp
 The following are read-only properties:
-.Bl -tag -width "unsupported@guid"
+.Bl -tag -width "last_scrubbed_txg"
 .It Sy allocated
 Amount of storage used within the pool.
 See
@@ -57,6 +57,21 @@ See
 and
 .Sy free
 for more information.
+.It Sy available
+The amount of free space available in the pool, adjusted for raidz parity
+overhead.
+The
+.Sy available
+property is calculated as:
+.Pp
+.Sy usable - used
+.Pp
+See
+.Sy usable ,
+.Sy used ,
+and
+.Sy free
+for more information.
 .It Sy bcloneratio
 The ratio of the total amount of storage that would be required to store all
 the cloned blocks without cloning to the actual storage used.
@@ -184,6 +199,21 @@ Information about unsupported features that are enabled on the pool.
 See
 .Xr zpool-features 7
 for details.
+.It Sy usable
+Estimate of total storage pool size, adjusted for raidz parity overhead.
+The adjustment assumes a fixed 128KiB record size to compute a data-to-parity
+ratio.
+.Sy usable
+is a heuristic for allocation and should not be interpreted as an exact measure
+of usable space.
+.It Sy used
+Estimate of storage used within the storage pool, adjusted for raidz parity
+overhead.
+The adjustment assumes a fixed 128KiB record size to compute a data-to-parity
+ratio.
+.Sy used
+is a heuristic for allocation and should not be interpreted as an exact measure
+of used space.
 .El
 .Pp
 The space usage properties report actual physical space available to the
@@ -201,6 +231,121 @@ For non-full pools of a reasonable size, these effects should be invisible.
 For small pools, or pools that are close to being completely full, these
 discrepancies may become more noticeable.
 .Pp
+The following properties are read-only metrics for allocation classes:
+.Bl -ohang
+.It Xo Sy class_dedup_allocated , class_dedup_available , class_dedup_capacity ,
+.Sy class_dedup_expandsize , class_dedup_fragmentation , class_dedup_free ,
+.Sy class_dedup_size , class_dedup_usable , class_dedup_used
+.Xc
+.Bd -ragged -offset Ds -compact
+Space usage properties of the pool's
+.Sy dedup
+metaslab allocator class.
+.Ed
+.It Xo Sy class_elog_allocated , class_elog_available , class_elog_capacity ,
+.Sy class_elog_expandsize , class_elog_fragmentation , class_elog_free ,
+.Sy class_elog_size , class_elog_usable , class_elog_used
+.Xc
+.Bd -ragged -offset Ds -compact
+Space usage properties of the pool's
+.Sy embedded_log
+metaslab allocator class.
+.Ed
+.It Xo Sy class_log_allocated , class_log_available , class_log_capacity ,
+.Sy class_log_expandsize , class_log_fragmentation , class_log_free ,
+.Sy class_log_size , class_log_usable , class_log_used
+.Xc
+.Bd -ragged -offset Ds -compact
+Space usage properties of the pool's
+.Sy log
+metaslab allocator class.
+.Ed
+.It Xo Sy class_normal_allocated , class_normal_available ,
+.Sy class_normal_capacity , class_normal_expandsize ,
+.Sy class_normal_fragmentation , class_normal_free , class_normal_size ,
+.Sy class_normal_usable , class_normal_used
+.Xc
+.Bd -ragged -offset Ds -compact
+Space usage properties of the pool's
+.Sy normal
+metaslab allocator class.
+.Ed
+.It Xo Sy class_special_allocated , class_special_available ,
+.Sy class_special_capacity , class_special_expandsize ,
+.Sy class_special_fragmentation , class_special_free , class_special_size ,
+.Sy class_special_usable , class_special_used
+.Xc
+.Bd -ragged -offset Ds -compact
+Space usage properties of the pool's
+.Sy special
+metaslab allocator class.
+.Ed
+.It Xo Sy class_special_elog_allocated , class_special_elog_available ,
+.Sy class_special_elog_capacity , class_special_elog_expandsize ,
+.Sy class_special_elog_fragmentation , class_special_elog_free ,
+.Sy class_special_elog_size , class_special_elog_usable ,
+.Sy class_special_elog_used
+.Xc
+.Bd -ragged -offset Ds -compact
+Space usage properties of the pool's
+.Sy special_embedded_log
+metaslab allocator class.
+.Ed
+.El
+.Pp
+Each allocation class is described by these values:
+.Bl -tag -width "fragmentation"
+.It Sy allocated
+Amount of storage used within the allocation class.
+.It Sy available
+Estimate of free space available in the allocation class, adjusted for raidz
+parity overhead.
+The adjustment assumes a fixed 128KiB record size to compute a data-to-parity
+ratio.
+.Sy available
+is a heuristic for allocation and should not be interpreted as an exact measure
+of usable space.
+Actual usable space depends on a variety of factors such as dataset record size
+and compression.
+.It Sy capacity
+Percentage of allocation class space used.
+.It Sy expandsize
+Amount of uninitialized space within the allocation class that can be used to
+increase the capacity of the allocator.
+See the pool-wide
+.Sy expandsize
+property.
+.It Sy fragmentation
+The amount of free space fragmentation in the allocation class.
+See the pool-wide
+.Sy fragmentation
+property.
+.It Sy free
+The amount of free space available in the allocation class.
+This value is not adjusted for factors such as dataset record size, compression,
+or raidz parity overhead.
+See the pool-wide
+.Sy free
+property.
+.It Sy size
+Total size of the allocation class.
+.It Sy usable
+Estimate of total allocation class size, adjusted for raidz parity overhead.
+The adjustment assumes a fixed 128KiB record size to compute a data-to-parity
+ratio.
+.Sy usable
+is a heuristic for allocation and should not be interpreted as an exact measure
+of usable space.
+.It Sy used
+Estimate of storage used within the allocation class, adjusted for raidz parity
+overhead.
+The adjustment assumes a fixed 128KiB record size to compute a data-to-parity
+ratio.
+.Sy used
+is a heuristic for allocation and should not be interpreted as an exact measure
+of used space.
+.El
+.Pp
 The following property can be set at creation time and import time:
 .Bl -tag -width Ds
 .It Sy altroot