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Enable fstrim.timer by default

Summary

Enabling fstrim.timer will cause fstrim.service to execute weekly, which in turn executes /usr/sbin/fstrim --fstab --verbose --quiet


Owner

Current status

  • Targeted release: Fedora 32
  • Last updated: 2019-12-19
  • Tracker bug: <will be assigned by the Wrangler>
  • Release notes tracker: <will be assigned by the Wrangler>

Detailed Description

Some users experience slow downs in certain flash storage devices, which can be alleviated by issuing a periodic fstrim command to the mounted file system. Devices and file systems that don't support fstrim are unaffected.

fstrim acts only on mounted filesystems listed in fstab. On supported hardware (SD Card, SSD, NVMe), thin provisioned virtual storage, and file systems (ext4, XFS, Btrfs, f2fs, but excluding FAT16/32), the underlying physical storage device's firmware is informed about unused blocks. This hinting can make wear leveling and block erasure more efficient.

Some devices do not support "queued trim" and there may be a brief (seconds) pause as the drive firmware acts upon command issuance. It's expected most users won't notice this. The timer will execute Monday at 00:00 local time. If the system is inactive at this time, it will be run immediately upon becoming active again (upon wake from suspend, during or very soon after boot).

Benefit to Fedora

This is an optimization to the storage stack, and may help improve performance and wear leveling for some devices.

In a way this is overdue on Fedora, as it's been the default behavior on other distributions for a while (at least Ubuntu and openSUSE). At least it has been a well tested optimization.


Scope

  • Proposal owners:

Upon approval, submit a PR for fedora-release, modifying 90-default.preset to enable fstrim.timer

  • Other developers:

strim.timer is provided by util-linux, notify util-linux maintainer

https://bugzilla.redhat.com/show_bug.cgi?id=1785041


  • Release engineering: #9116
  • Policies and guidelines: N/A
  • Trademark approval: N/A

Upgrade/compatibility impact

fstrim.timer will be enabled on upgrade. An upgraded system should exhibit the same behaviors as a clean installed system.

How To Test

The low level function of the fstrim command and fstrim.service is well understood and tested already, all Fedora needs to test is that the timer is enabled following clean installation and upgrades: Preliminaries:

  • Clean install Fedora 32, any edition or spin; or
  • Upgrade from Fedora 30 or Fedora 31, any edition or spin, to Fedora 32

Confirm:

  • sudo systemctl list-timers
  • Confirm fstrim.timer is listed under UNITS, and is next scheduled for Monday 00:00:00
  • Anytime following the NEXT time, sudo systemctl status fstrim.timer

Example, should apply in all cases: Dec 18 13:48:54 fmac.local systemd[1]: fstrim.service: Succeeded.

Full example on a device with an SSD and filesystem supporting trim: ` $ sudo systemctl status fstrim.service ● fstrim.service - Discard unused blocks on filesystems from /etc/fstab 

  Loaded: loaded (/usr/lib/systemd/system/fstrim.service; static; vendor preset: disabled)
  Active: inactive (dead) since Wed 2019-12-18 13:48:54 MST; 15min ago
    Docs: man:fstrim(8)
 Process: 3870 ExecStart=/usr/sbin/fstrim --fstab --verbose --quiet (code=exited, status=0/SUCCESS)
Main PID: 3870 (code=exited, status=0/SUCCESS)
     CPU: 1.387s

Dec 18 13:48:48 fmac.local systemd[1]: Starting Discard unused blocks on filesystems from /etc/fstab... Dec 18 13:48:54 fmac.local fstrim[3870]: /: 32 GiB (34409328640 bytes) trimmed on /dev/sda4 Dec 18 13:48:54 fmac.local systemd[1]: fstrim.service: Succeeded. Dec 18 13:48:54 fmac.local systemd[1]: Started Discard unused blocks on filesystems from /etc/fstab. Dec 18 13:48:54 fmac.local systemd[1]: fstrim.service: Consumed 1.387s CPU time. ` Regardless of configuration, there should be no errors.

User Experience

Most users will not notice the change. Some will notice improved performance of flash storage devices, and more efficient use of thinly provisioned storage.

This does NOT affect all storage. Only file systems listed in fstab will be affected.

If the user/admin wants fstrim to apply to all storage, they should copy the original fstrim.service unit file, replacing --fstab with --all which will then run fstrim weekly on all mounted file systems. And use this modified unit file as a drop in service unit. See https://www.freedesktop.org/software/systemd/man/systemd.unit.html

Contingency Plan

  • Contingency mechanism: Owner will revert the change
  • Contingency deadline: final freeze
  • Blocks release? No
  • Blocks product? No

Documentation

man fstrim


Release Notes

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