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Btrfs/ZFS/bcachefs under workloads classic benchmarks skip

23 pointsby 1h agobartosz.fenski.pl
18 comments
39m agoHN ↗

@farlight assuming that you're the creator do you think you'd be able to rework the HTML/CSS? I'm sure you've got good data but speaking on behalf of my eyeballs, the results page is... hard to read!

35m agoHN ↗

2G of random garbage is written directly onto one member device (behind the filesystem's back, offset 1G — python injector; uutils dd mis-seeks on dm devices), caches dropped, then a full scrub: btrfs scrub -B, zpool scrub + wait, bcachefs scrub, md/lvm sync-action 'check' (which can only COUNT mismatches — no checksums to know which copy is right).

I'm not sure that nuking 2G of the underlying block device is a recoverable error on any filesystem that I'm aware of? Can you confirm if any ofthe filesystems really came out of the other side in a usable state after scrubbing?

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Trivial-op p99, idle (ms) # A trivial operation — one 4k write + fsync every 200ms (like a shell appending history or an editor updating its swap file) — run alone for 10s. p99 of the fsync completion

In fact, if it's OK for me to ask, are any of the metrics tht you used standard industry metrics? It looks like several of the tests are bypassing the kernel's page cache? -- which I worry may fall into the trap of "I modified the system to be unrepresentative of reality and then tested it".

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kernel 7.0.0-1012-azure

Can you confirm if you tested on a bare metal machine? were you the only tenant?

31m agoHN ↗

1 device out of the replica set I’m assuming so all of them should recover.

29m agoHN ↗

The integrity check is only on the tests which are either RAID or the filesystem equivalent.

28m agoHN ↗

Except for the fact that the developer has sabotaged the project into being removed from mainline?

33m agoHN ↗

For peace of mind I'm still using zfs (since the last 15+ years) but I'm definitely not impressed by the performance...

29m agoHN ↗

Different tools for different jobs; use ZFS for your data store and ext4 for your primary drive.

23m agoHN ↗

CI runs use loop devices on shared ephemeral VMs (one VM per filesystem): compare shapes and ratios, not absolute MB/s. Each job records a host-calibration anchor — see the table.

I think if you're not using baremetal for such tests, it's likely that the results are simply not comparable at all? What if another tenant is also using the disk?

17m agoHN ↗

It's a fair point but it's also possible the person running the tests has a dedicated test hypervisor for this , so that different configurations of filesystems and VMs can be created and destroyed quickly in an automated manner.

If it's something as simple as a KVM hypervisor that only runs 1 test VM at a time (with no other load from anything else other than the basic systemd daemons, ssh daemon etc running on the hypervisor), the results could be very close to bare metal.

I can see it being very time consuming and annoying to do repeated manual bare metal OS installs and new partitioning/filesystem creation for such a large variety of tests.

The author does also say that performance isn't really the main thing but rather, data integrity:

https://github.com/fenio/modern-fs-benchmark

7m agoHN ↗

compare shapes and ratios, not absolute MB/s

In this case, given that the author's own disclaimer (above) already disclaims the numeric readings, I'm not sure how it's possible to make any inference on "shapes and ratios" derived from the numeric readings.

5m agoHN ↗

I can see it being very time consuming and annoying to do repeated manual bare metal OS installs.

Well don't do that then. There's lots of other options. Probably the simplest is a single bare metal install on a simple filesystem on one device. run the filesystems under test on other storage dedicated to testing.

You could also boot into a network install and use local storage exclusively for testing.

2m agoHN ↗

Yes exactly. The issueThe epherrality of the VMs isn't an issue, it's the _shared_ part that's the concern here. Going by the fact that the kernel is listed as "kernel 7.0.0-1012-azure" I feel like it's a fair risk that there may have been noisy neighbours.

8m agoHN ↗

I think the reviews should also include the social aspect of these filesystems...

There is and have been many promising and exciting FS to replace the old boring ones, but for storage you not only want to avoid technical issues but also maintainer(s) drama...