On 9/5/20 5:29 AM, Neal Becker wrote:
If BTRFS is to become fedora default, we should consider this?
"BTRFS relatime vs. noatime - Huge Performance Difference - linux"
https://www.reddit.com/r/linux/comments/imgler/btrfs_relatime_vs_noatime_huge_performance/?utm_source=amp&utm_medium=&utm_content=post_body
The *performance* difference is probably vastly overstated by people who
haven't actually compared btrfs to other filesystems. At least, I keep
seeing this come up, but haven't yet seen anyone offer a comparison to
any other filesystem, and I suspect that it is a myth.
I copied 150,000 files from btrfs to ext4 with atime updates, and the
same transfer with no atime updates. I did the same process with ext4 to
ext4.
The performance impact of atime updates on ext4 was 9.6% (31.65s ->
28.614s). The performance impact of atime updates on btrfs was 3.86%
(29.626s -> 28.482s).
This isn't a scientific test, and I'm not going to argue henceforth that
btrfs performs better than ext4, but the test does suggest that btrfs
with relatime isn't the "sky is falling" performance disaster that
people are making it out to be.
|#!/bin/sh bf1=/home/input bf2=/home/output dd if=/dev/zero of=$bf1
bs=1M count=10000 dd if=/dev/zero of=$bf2 bs=1M count=10000 losetup
/dev/loop1 $bf1 losetup /dev/loop2 $bf2 mkfs.btrfs /dev/loop1 mkfs.ext4
/dev/loop2 mkdir /mnt/input mkdir /mnt/output mount /dev/loop1
/mnt/input mount /dev/loop2 /mnt/output rsync -aHS /home/flatpak
/mnt/input find /mnt/input -exec touch -h -a -d 'Jan 1 2020' {} + time
rsync -aHS /mnt/input/ /mnt/output umount /mnt/output mkfs.ext4
/dev/loop2 mount /dev/loop2 /mnt/output # atime is already updated on
/mnt/input, so it's not strictly necessary to remount it with noatime
time rsync -aHS /mnt/input/ /mnt/output umount /mnt/input umount
/mnt/output rmdir /mnt/input rmdir /mnt/output losetup -d /dev/loop1
losetup -d /dev/loop2 rm $bf1 rm $bf2|
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