Re: Fedora 34 Change: Enable btrfs transparent zstd compression by default (System-Wide Change proposal)
On Fri, Jan 1, 2021 at 11:31 AM Artem Tim <ego.cordatus(a)gmail.com> wrote:
It's faster. Here is some benchmark with different zstd compression ratios
https://lkml.org/lkml/2019/1/28/1930. Could be outdated a little bit though.
But for HDD it makes sense to increase it probably. And IIRC Chris wrote about such
plans.
There are ideas but it's difficult because the kernel doesn't expose
the information we really need to make an automatic determination.
sysfs commonly misreports rotational devices as being non-rotational
and vice versa. Since this is based on the device self-reporting, it's
not great.
I use zstd:1 for SSD/NVMe. And zstd:3 (which is the same as not
specifying a level) for HDD/USB sticks/eMMC/SD Card. For the more
archive style of backup, I use zstd:7. But these can all be mixed and
matched, Btrfs doesn't care. You can even mix and match algorithms.
Anyway, compress=zstd:1 is a good default. Everyone benefits, and I'm
not even sure someone with a very fast NVMe drive will notice a slow
down because the compression/decompression is threaded.
I expect if we get the "fast" levels (the negative value levels) new
to zstd in the kernel, that Btrfs will likely remap its level 1 to one
of the negative levels, and keep level 3 set to zstd 3 (the default).
So we might actually see it get even faster at the cost of some
compression ratio. Given this possibility, I think level 1 is the best
choice as a default for Fedora.
--
Chris Murphy