99-usb-sata-write-cache.rules

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  • 99-usb-sata-write-cache.rules 1.0 KB
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DownloadRawudev rules · 11 lines · 1.0 KB

From Add a USB SSD to a Raspberry Pi 5 running Home Assistant OS. MIT licence: LICENSE.

usb-ssd-pi5/99-usb-sata-write-cache.rules

# USB drives whose USB chip hides the drive's write cache, so Linux stops sending cache flushes:
# - UGREEN USB-SATA adapters (Realtek RTL9201, 0bda:9201) with UAS off (usb-storage.quirks=0bda:9201:u
#   in cmdline.txt) report the drive's write cache as off.
# - WD Elements Portable 2 TB (1058:1048, WD's own chip) has no caching mode page, so the kernel
#   assumes write through.
# The drives keep their cache on (smartctl -g wcache), so an fsync could sit in the drive's cache and be
# lost in a power cut. "temporary" changes only the kernel's view: it sends flushes again, nothing is
# written to the drive. See raspberry-pi/README.md (UAS off and write cache).
# On the Pi: /etc/udev/rules.d/99-usb-sata-write-cache.rules (HAOS keeps it on the overlay partition).
ACTION=="add|change", SUBSYSTEM=="scsi_disk", ATTRS{idVendor}=="0bda", ATTRS{idProduct}=="9201", ATTR{cache_type}="temporary write back"
ACTION=="add|change", SUBSYSTEM=="scsi_disk", ATTRS{idVendor}=="1058", ATTRS{idProduct}=="1048", ATTR{cache_type}="temporary write back"