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Alexander Motin be1e991a1a
Allow and prefer special vdevs as ZIL
Before this change ZIL blocks were allocated only from normal or
SLOG vdevs.  In typical situation when special vdevs are SSDs and
normal are HDDs it could cause weird inversions when data blocks
are written to SSDs, but ZIL referencing them to HDDs.

This change assumes that special vdevs typically have much better
(or at least not worse) latency than normal, and so in absence of
SLOGs should store ZIL blocks.  It means similar to normal vdevs
introduction of special embedded log allocation class and updating
the allocation fallback order to: SLOG -> special embedded log ->
special -> normal embedded log -> normal.

The code tries to guess whether data block is going to be written
to normal or special vdev (it can not be done precisely before
compression) and prefer indirect writes for blocks written to a
special vdev to avoid double-write.  For blocks that are going to
be written to normal vdev, special vdev by default plays as SLOG,
reducing write latency by the cost of higher special vdev wear,
but it is tunable via module parameter.

This should allow HDD pools with decent SSD as special vdev to
work under synchronous workloads without requiring additional
SLOG SSD, impractical in many scenarios.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Rob Norris <rob.norris@klarasystems.com>
Reviewed-by: Paul Dagnelie <paul.dagnelie@klarasystems.com>
Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes #17505
2025-07-18 18:44:14 -07:00
.github CI: Add CentOS Stream 9/10 to the FULL_OS runner list 2025-07-15 10:00:35 -07:00
cmd Allow and prefer special vdevs as ZIL 2025-07-18 18:44:14 -07:00
config Define sops->free_inode() to prevent use-after-free during lookup 2025-07-18 08:45:13 -07:00
contrib Add templated zfs-mount@.service 2025-07-03 14:24:07 -07:00
etc Add templated zfs-mount@.service 2025-07-03 14:24:07 -07:00
include Allow and prefer special vdevs as ZIL 2025-07-18 18:44:14 -07:00
lib libzpool: tunable-based option interface for zdb/ztest 2025-07-15 15:47:03 -07:00
man Allow and prefer special vdevs as ZIL 2025-07-18 18:44:14 -07:00
module Allow and prefer special vdevs as ZIL 2025-07-18 18:44:14 -07:00
rpm Add templated zfs-mount@.service 2025-07-03 14:24:07 -07:00
scripts mod.h: make consistent across all three platforms 2025-07-15 15:46:14 -07:00
tests Fix zdb pool/ with -k 2025-07-15 17:01:49 -07:00
udev Update 69-vdev.rules.in 2025-05-21 10:05:11 -07:00
.editorconfig Add an .editorconfig; document git whitespace settings 2020-01-27 13:32:52 -08:00
.gitignore Packaging: Auto-generate changelog during configure (#15528) 2023-11-16 08:58:47 -08:00
.gitmodules .gitmodules: link to openzfs github repository 2021-04-12 09:37:23 -07:00
.mailmap AUTHORS/mailmap: update with new contributors 2025-05-13 09:24:03 -07:00
AUTHORS AUTHORS/mailmap: update with new contributors 2025-05-13 09:24:03 -07:00
autogen.sh Ubuntu 22.04 integration: ShellCheck 2022-11-18 11:24:48 -08:00
CODE_OF_CONDUCT.md Documentation corrections 2022-12-22 11:34:28 -08:00
configure.ac Linux build: handle CONFIG_OBJTOOL_WERROR=y 2025-06-16 08:12:09 -07:00
copy-builtin copy-builtin: add hooks with sed/>> 2022-05-10 10:17:43 -07:00
COPYRIGHT Fix typos 2020-06-09 21:24:09 -07:00
LICENSE Update build system and packaging 2018-05-29 16:00:33 -07:00
Makefile.am spdxcheck: program to check SPDX license tags 2025-03-13 17:57:51 -07:00
META Linux 6.15 compat: META 2025-05-28 16:28:02 -07:00
NEWS Fix NEWS file 2020-08-26 21:44:41 -07:00
NOTICE Update build system and packaging 2018-05-29 16:00:33 -07:00
README.md FreeBSD: remove support for FreeBSD < 13.0-RELEASE (#16372) 2024-08-05 16:56:45 -07:00
RELEASES.md Update RELEASES.md LTS release to 2.2 2025-01-17 11:04:36 -05:00
TEST Remove CI builder customization from TEST 2020-03-16 10:46:03 -07:00
zfs.release.in Move zfs.release generation to configure step 2012-07-12 12:22:51 -07:00

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OpenZFS is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the OpenZFS community. This repository contains the code for running OpenZFS on Linux and FreeBSD.

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Official Resources

Installation

Full documentation for installing OpenZFS on your favorite operating system can be found at the Getting Started Page.

Contribute & Develop

We have a separate document with contribution guidelines.

We have a Code of Conduct.

Release

OpenZFS is released under a CDDL license. For more details see the NOTICE, LICENSE and COPYRIGHT files; UCRL-CODE-235197

Supported Kernels

  • The META file contains the officially recognized supported Linux kernel versions.
  • Supported FreeBSD versions are any supported branches and releases starting from 13.0-RELEASE.