On Mon, Feb 24, 2020 at 12:55:05PM +0100, Matthias G. Eckermann wrote: > Hello Axel, > > On 2020-02-24 T 11:41 +0100 Axel Braun wrote: > > Am Sonntag, 23. Februar 2020, 22:36:33 CET schrieb Matthias G. Eckermann: > > > On 2020-02-23 T 17:03 +0100 Axel Braun wrote: > > > > > Except that I feel that one should not use btrfs on a 32GB > > > > SD card > > > > > > one of the reasons to use btrfs for the RPi image (I know > > > that at least for SUSE Linux Enterprise) is that it is > > > compressed and thus the low IO-throughput of the SD card > > > interface is accelerated; assuming a compression rate for > > > the OS part of more than 30%, the performance factor should > > > be similar for reads and writes. > > > > Thanks for the information! > > > > So the old rule (i remember some discussions on the factory > > mailing list from some time ago) that btrfs on less than 40GB > > is not recommended, is not valid any longer? > > well. I would have never called this "40GiB" a "rule", but more > a "recommendation" for a btrfs root filesystem *with* snapshots > enabled, and this recommendation has a *lot* of safety buffer > included. > > Mind that this heavily depends on the > - distribution > and > - your personal way of applying updates. > > To add some details: > > * For a Tumbleweed with add-hoc updates enabled, I would > rate 40 GiB the lower limit, indeed, better more, as > you have a lot of change, thus lots of snapshots and > lots of metadata. > > * For a Leap or SUSE Linux Enterprise with, let's say, > planned weekly updates, you can easily work with a > btrfs filesystem as small as twice the size of the OS > installation, or for an extra buffer three times: > > MINIMAL_SIZE=$(( 3* $( du -msx / | cut -d'/' -f1) )) > > I personally run (all my) systems with a 32 GiB root > filesystem with snapshots enabled, and the number of > snapshots limited to 8 in total. > > That said, for a Raspberry Pi and an SD card, I would recommend > to apply updates rather carefully and not in tumbleweed style, > because the SD card might not like this too much:-/ Thus, a > 32 GiB filesystem (with compression enabled this is equivalent > to 42 GiB or more effectively) should be very comfortable.
To move even closer to a real sytem: I'm running btrfs on 12GB https://build.opensuse.org/package/show/home:duwe:Teres-I/Teres-I-image without snapshotting, and it "works". In quotes because I have not done comparisons or even benchmarks vs. f2fs or ext4. Torsten -- To unsubscribe, e-mail: opensuse-arm+unsubscr...@opensuse.org To contact the owner, e-mail: opensuse-arm+ow...@opensuse.org
