On Sat, 2020-06-27 at 13:34 -0600, Chris Murphy wrote: > On Sat, Jun 27, 2020 at 11:59 AM Konstantin Kharlamov > <hi-angel@xxxxxxxxx> wrote: > > On Sat, 2020-06-27 at 17:00 +0300, Konstantin Kharlamov wrote: > > > Another reason worth mentioning: BTRFS per se is slow. If you look at > > > benchmarks > > > on Phoronix comparing BTRFS with others, BTRFS is rarely even on par with > > > them. > > > > Btw, I should also add here: it may be clear that in ideal situtation BTRFS > > will > > always be slower than non-COW file systems. The problem however, it is not > > even > > on par with the other open-source COW file system, which is ZFS. > > > > Some months ago at my dayjob I was performing benchmarks, and out of > > curiosity I > > also compared latest released (as of then, it was 5.6 kernel) BTRFS with > > latest > > master of ZFS (which was of a commit b29e31d80 and a kernel 5.4). > > > > The setup was a RAID5 on 10 SSDs, and a benchmark was three 20-minutes long > > runs > > of vdbench with random 70% reads and random 30% writes. For BTRFS I also > > used > > `space_cache=v2` mount option. Results were: > > > > FS | run 1, IOPS | run 2, IOPS | run 3, IOPS > > BTRFS | 65723.9 | 56474.5 | 55090.2 > > ZFS | 96846.1 | 79797.9 | 76249.4 > > For the sake of the argument I will accept the above as facts. > > But raid5 correlates to the desktop how? Does my desktop workload need > 96K IOPS? Do I notice the difference even if it can be measured? And > the vdbench command used is? And this particular vdbench command > produces a benchmark that mimics what workload found on the desktop? > There is no hand waving away the relevance of these questions if > you're going to propose performance benchmarks are relevant. Fair enough. > > So, summing up this and my previous mail overall, I do not think that for > > ordinary desktop BTRFS is currently any good, compared to EXT4 or XFS. > > Not persuasive. > > I think your argument is improved if you say we need more and better > benchmarking that mimics the actual workloads we care about; or times > a set of test cases that people can try themselves and reproduce. > > I use a variety of OS's on a variety of hardware, including the laptop > I'm using now which is Fedora and Windows dual boot and I'm not > suspicious of performance issues of any kind: Fedora's faster, period. > Might it seem even faster if it were ext4? I've done it, and I don't > think so. So how do you produce a benchmark that accounts for the > user's perception of performance, rather than just raw performance? > Because maybe btrfs is faster. Maybe it's slower. But does it matter? > > If it took 5 seconds for GNOME Terminal to launch I'd be mad. 21 > seconds is just nonsense. So yes it does matter, but what's the > threshold at which it matters? These benchmarks aren't capturing > either the reality or the feeling. So we need better (more relevant) > benchmarks to have a proper discussion. > > For the vast majority of things I'm doing, even if it were the case > that some things are slower, *I* am still much slower than whatever > extra latency there may be. And same goes for the reverse, if btrfs > compression makes some things slightly faster, will I notice? I don't > know. But is that the only metric? I know for sure my hardware is > doing far fewer writes (and reads for that matter), so there is less > wear and tear on the hardware. Is that saving me 50 cents or $50 over > the life of the hardware? I don't know but I do know it's better than > no compression, overall. Thank you, I see your point. Since it seems to also be present in the reply to my other mail, let's continue there. _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx
