I’m setting up storage on a new system, and recently learned that there are different options for checksum hash algorithms on btrfs. It appears that xxhash
is generally faster than the default crc32c
on AMD Ryzen systems, and is 64-bit instead of 32-bit. So, I created my new filesystem with that. I can’t see, though, how to see that I have in fact done this correctly. It seems like probably something in the btrfs
command will tell me, but I can’t find it.
$ dmesg | grep -i btrf
[ 2.687578] Btrfs loaded, crc32c=crc32c-generic
Looks like dmesg
could show you. I see only 1 line so I’m not sure it is per filesystem.
Also found this
cat /sys/fs/btrfs/$(blkid info -o value -s UUID $DEVICE)/checksum
but does not work here.
I have only one btrfs volume at the moment.
This works for me. Did you set DEVICE
to the desired value? And blkid
will want to be root. On a Fedora system, you should be able to get the UUID out of /etc/fstab
instead of using blkid
, if you like. There different ways to approach this — sudo btrfs filesystem show
would also work.
On my system, once I have UUID
set to the device of interest, it works fine. Or you can do
cat /sys/fs/btrfs/*/checksum
with a wildcard to see all filesystems.
Got it, that works.
Got output crc32c (crc32c-intel)
which differs from the dmesg output.
On mine it’s xxhash64 (xxhash64-generic)
, which is good because that’s what I’d intended to use. For backup drives, I might use sha256
even though it’s slow.
Anyway thanks for your help — I wouldn’t have thought to look there!
Now I’m curious, what do you see after dmesg |grep Btrfs
?
Same Btrfs loaded, crc32c=crc32c-generic
. But I haven’t rebooted since I created the xxhash
filesystem, so I’m curious to see what will happen!
Btrfs loaded, crc32c=crc32c-generic
This just lets us know which crcr32c code is being used, because there’s more than one.
$DEVICE
needs to be replaced with the device node you’re inquiring about. And also sudo
is needed for the blkid command. e.g.
sudo cat /sys/fs/btrfs/$(blkid info -o value -s UUID /dev/nvme0n1p7)/checksum
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