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180 lines
4.2 KiB
Groff
180 lines
4.2 KiB
Groff
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.\" SPDX-License-Identifier: CDDL-1.0
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.\"
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.\" This file and its contents are supplied under the terms of the
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.\" Common Development and Distribution License ("CDDL"), version 1.0.
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.\" You may only use this file in accordance with the terms of version
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.\" 1.0 of the CDDL.
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.\"
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.\" A full copy of the text of the CDDL should have accompanied this
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.\" source. A copy of the CDDL is also available via the Internet at
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.\" http://www.illumos.org/license/CDDL.
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.\"
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.\" Copyright (c) 2026 Christos Longros. All rights reserved.
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.\"
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.Dd March 14, 2026
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.Dt ZARCSUMMARY 1
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.Os
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.
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.Sh NAME
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.Nm zarcsummary
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.Nd print ZFS ARC and subsystem statistics
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.Sh SYNOPSIS
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.Nm
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.Op Fl adghr
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.Op Fl p Ar page
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.Op Fl s Ar section
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.
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.Sh DESCRIPTION
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.Nm
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collects statistics from the running kernel and prints a human-readable
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report on the state of the ZFS Adaptive Replacement Cache
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.Pq ARC
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and several related subsystems.
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The output is a snapshot; for periodic sampling, use
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.Xr zarcstat 1
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instead.
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.Pp
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When invoked without arguments,
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.Nm
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prints all sections in sequence.
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A single section may be selected with the
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.Fl s
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option.
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.Pp
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The report is organized into the following sections:
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.Bl -tag -offset Ds -width "tunables"
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.It Sy arc
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Current and target ARC sizes, the split between the Most Recently Used
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.Pq MRU
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and Most Frequently Used
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.Pq MFU
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lists, overall hit and miss ratios, compression savings, and whether the
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ARC is experiencing memory pressure.
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.It Sy archits
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Breakdown of ARC hits and misses by demand reads versus prefetches
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and data versus metadata.
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.It Sy dmu
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Data Management Unit predictive prefetcher statistics, including stream
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hits, misses, and I/O issued ahead of and behind the current stream.
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.It Sy l2arc
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Level-2 ARC statistics for any cache devices attached to imported pools.
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This section only appears when an L2ARC device is present and covers
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bytes read and written, hit rates, and eviction activity.
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.It Sy spl
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Solaris Porting Layer memory allocator statistics.
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This section is only available on Linux.
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.It Sy tunables
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Current values of kernel tunables that govern ARC behavior, including
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.Va zfs_arc_max
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and
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.Va zfs_arc_min .
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Combining this section with
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.Fl d
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adds a brief explanation of each tunable.
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.It Sy zil
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ZFS Intent Log statistics: committed transaction counts, flush requests
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to stable storage, and the byte-level split between normal vdevs and
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any separate log
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.Pq SLOG
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device.
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.El
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.
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.Sh OPTIONS
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.Bl -tag -width "-s"
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.It Fl a , -alternate
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Use an alternate layout for the tunables and SPL sections.
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.It Fl d , -description
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Print a short description next to each tunable and SPL entry.
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.It Fl h , -help
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Display a help message.
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.It Fl g , -graph
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Print an ASCII graph of current ARC use and exit.
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.It Fl p Ar page , Fl -page Ar page
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Print a section by its legacy page number.
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.Sy Deprecated ;
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use
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.Fl s
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instead.
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.It Fl r , -raw
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Dump all available data with minimal formatting.
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.It Fl s Ar section , Fl -section Ar section
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Print only the named section.
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See
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.Sx DESCRIPTION
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for the list of valid section names.
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.El
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.
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.Sh ENVIRONMENT
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.Bl -tag -width "FreeBSD"
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.It Sy Linux
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Statistics are read from
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.Pa /proc/spl/kstat/zfs/ .
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.It Fx
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Statistics are read via
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.Xr sysctl 3
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from the
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.Va vfs.zfs
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and
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.Va kstat.zfs.misc
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trees.
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The
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.Pa py-sysctl
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package must be installed for
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.Nm
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to function.
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.El
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.
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.Sh EXIT STATUS
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.Ex -std
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.
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.Sh EXAMPLES
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Print the full report:
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.Dl # zarcsummary
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.Pp
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Display only ARC size and hit rate information:
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.Dl # zarcsummary -s arc
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.Pp
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Show a visual overview of ARC health:
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.Dl # zarcsummary -g
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.Pp
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Search for all statistics containing
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.Dq hit :
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.Dl # zarcsummary -r | grep hit
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.Pp
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Review all tunables with their descriptions:
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.Dl # zarcsummary -d -s tunables
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.
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.Sh SEE ALSO
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.Xr zarcstat 1 ,
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.Xr zpool-status 8
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.
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.Sh HISTORY
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.Nm
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originated as a Perl script called
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.Nm arc_summary ,
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written by
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.An Ben Rockwood
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in 2008 for Solaris.
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.An Martin Matuska
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ported it to
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.Fx
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in 2010, and
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.An Jason J. Hellenthal
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took over maintenance.
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.An Scot W. Stevenson
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contributed a full rewrite in Python 3 in 2017, introducing the
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.Fl g ,
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.Fl r ,
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and
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.Fl s
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options along with the section-based output layout.
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The tool was renamed from
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.Nm arc_summary
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to
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.Nm zarcsummary
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in 2025 to align with the OpenZFS command naming convention.
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.
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.Sh AUTHORS
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This manual page was written by
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.An Christos Longros Aq Mt chris.longros@gmail.com .
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