ceremcem edited a comment on issue #611:
URL:
https://github.com/apache/couchdb-documentation/issues/611#issuecomment-748539446
> Have you seen a significant CouchDB performance change when altering the
file setting? Alternatively, what does filefrag say on those files on a system
that has been in production for a while?
This needs to be measured. Luckily I have a production setup on BTRFS where
I forgot to change that CoW flag, so system was running without CoW flag
disabled for a year. I was experiencing lots of interesting issues with
database microservice, but that might not be related directly with this topic.
Let's see.
CouchDB 3.x on my Laptop in LXC container (Debian Buster, freshly
installed), with ~20K documents synced *after* `chattr +C /var/lib/couchdb`
with the `production server` :
```commands
root@couchdb-erik:/var/lib# find couchdb -type f -exec filefrag {} \;
couchdb/couchdb/_dbs.couch: 1 extent found
couchdb/couchdb/_nodes.couch: 1 extent found
couchdb/couchdb/shards/80000000-ffffffff/_users.1608348635.couch: 1 extent
found
couchdb/couchdb/shards/80000000-ffffffff/_replicator.1608348637.couch: 1
extent found
couchdb/couchdb/shards/80000000-ffffffff/test.1608349285.couch: 1 extent
found
couchdb/couchdb/shards/00000000-7fffffff/_users.1608348635.couch: 1 extent
found
couchdb/couchdb/shards/00000000-7fffffff/_replicator.1608348637.couch: 1
extent found
couchdb/couchdb/shards/00000000-7fffffff/test.1608349285.couch: 1 extent
found
couchdb/_dbs.couch: 5 extents found
couchdb/_nodes.couch: 1 extent found
couchdb/shards/80000000-ffffffff/_users.1608348635.couch: 1 extent found
couchdb/shards/80000000-ffffffff/_replicator.1608348637.couch: 3 extents
found
couchdb/shards/80000000-ffffffff/test.1608349285.couch: 1 extent found
couchdb/shards/80000000-ffffffff/foo2.1608351797.couch: 2 extents found
couchdb/shards/80000000-ffffffff/foo2.1608353430.couch.compact.meta: 2
extents found
couchdb/shards/80000000-ffffffff/foo2.1608353430.couch: 31 extents found
couchdb/shards/00000000-7fffffff/_users.1608348635.couch: 1 extent found
couchdb/shards/00000000-7fffffff/_replicator.1608348637.couch: 18 extents
found
couchdb/shards/00000000-7fffffff/test.1608349285.couch: 1 extent found
couchdb/shards/00000000-7fffffff/foo2.1608351797.couch: 2 extents found
couchdb/shards/00000000-7fffffff/foo2.1608353430.couch.compact.meta: 2
extents found
couchdb/shards/00000000-7fffffff/foo2.1608353430.couch: 20 extents found
```
CouchDB 3.x on my server in LXC container (Debian Buster, freshly
installed), with ~20K documents synced *after* `chattr +C /var/lib/couchdb`
with the `production server` :
```
root@aktos-couch4:/var/lib# find couchdb -type f -exec filefrag {} \;
couchdb/_dbs.couch: 2 extents found
couchdb/_nodes.couch: 1 extent found
couchdb/shards/80000000-ffffffff/_users.1608390062.couch: 1 extent found
couchdb/shards/80000000-ffffffff/_replicator.1608390062.couch: 3 extents
found
couchdb/shards/80000000-ffffffff/foo2.1608390979.couch.compact.meta: 3
extents found
couchdb/shards/80000000-ffffffff/foo2.1608390979.couch: 922 extents found
couchdb/shards/00000000-7fffffff/_users.1608390062.couch: 1 extent found
couchdb/shards/00000000-7fffffff/_replicator.1608390062.couch: 1 extent found
couchdb/shards/00000000-7fffffff/foo2.1608390979.couch.compact.meta: 6
extents found
couchdb/shards/00000000-7fffffff/foo2.1608390979.couch: 290 extents found
```
CouchDB 2.x on my server in LXC container (Debian Stretch), with ~20K
documents. This is my production server (where CoW is not disabled):
```
root@aktos-couch3:/var/lib# find couchdb -type f -exec filefrag {} \; | sort
-t":" -k 2 -n -r
couchdb/shards/c0000000-dfffffff/foo2.1576202327.couch: 8882 extents found
couchdb/shards/40000000-5fffffff/foo2.1576202327.couch: 8707 extents found
couchdb/shards/80000000-9fffffff/foo2.1576202327.couch: 3514 extents found
couchdb/shards/60000000-7fffffff/foo2.1576202327.couch: 2336 extents found
couchdb/shards/a0000000-bfffffff/foo2.1576202327.couch: 2320 extents found
couchdb/shards/00000000-1fffffff/foo2.1576202327.couch: 2210 extents found
couchdb/shards/e0000000-ffffffff/foo2.1576202327.couch: 2186 extents found
couchdb/shards/20000000-3fffffff/foo2.1576202327.couch: 2041 extents found
couchdb/.shards/60000000-7fffffff/foo2.1576202327_design/mrview/ff377ba3dcf6801401e64c4b47ee91f0.view:
825 extents found
couchdb/.shards/60000000-7fffffff/foo2.1576202327_design/mrview/60c0365cb541a047d8841256fb5104af.view:
824 extents found
couchdb/.shards/60000000-7fffffff/foo2.1576202327_design/mrview/54f171fe1f24ac4eb52ac24c85f9d8fc.view:
824 extents found
couchdb/.shards/a0000000-bfffffff/foo2.1576202327_design/mrview/54f171fe1f24ac4eb52ac24c85f9d8fc.view:
814 extents found
couchdb/.shards/a0000000-bfffffff/foo2.1576202327_design/mrview/ff377ba3dcf6801401e64c4b47ee91f0.view:
811 extents found
couchdb/.shards/a0000000-bfffffff/foo2.1576202327_design/mrview/60c0365cb541a047d8841256fb5104af.view:
810 extents found
couchdb/.shards/40000000-5fffffff/foo2.1576202327_design/mrview/ff377ba3dcf6801401e64c4b47ee91f0.view:
806 extents found
couchdb/.shards/40000000-5fffffff/foo2.1576202327_design/mrview/60c0365cb541a047d8841256fb5104af.view:
805 extents found
couchdb/.shards/00000000-1fffffff/foo2.1576202327_design/mrview/ff377ba3dcf6801401e64c4b47ee91f0.view:
788 extents found
couchdb/.shards/00000000-1fffffff/foo2.1576202327_design/mrview/60c0365cb541a047d8841256fb5104af.view:
788 extents found
couchdb/.shards/00000000-1fffffff/foo2.1576202327_design/mrview/54f171fe1f24ac4eb52ac24c85f9d8fc.view:
788 extents found
couchdb/.shards/20000000-3fffffff/foo2.1576202327_design/mrview/ff377ba3dcf6801401e64c4b47ee91f0.view:
782 extents found
couchdb/.shards/20000000-3fffffff/foo2.1576202327_design/mrview/54f171fe1f24ac4eb52ac24c85f9d8fc.view:
780 extents found
couchdb/.shards/20000000-3fffffff/foo2.1576202327_design/mrview/60c0365cb541a047d8841256fb5104af.view:
779 extents found
couchdb/.shards/c0000000-dfffffff/foo2.1576202327_design/mrview/60c0365cb541a047d8841256fb5104af.view:
759 extents found
couchdb/.shards/c0000000-dfffffff/foo2.1576202327_design/mrview/ff377ba3dcf6801401e64c4b47ee91f0.view:
758 extents found
couchdb/.shards/e0000000-ffffffff/foo2.1576202327_design/mrview/ff377ba3dcf6801401e64c4b47ee91f0.view:
737 extents found
couchdb/.shards/e0000000-ffffffff/foo2.1576202327_design/mrview/60c0365cb541a047d8841256fb5104af.view:
737 extents found
couchdb/.shards/e0000000-ffffffff/foo2.1576202327_design/mrview/54f171fe1f24ac4eb52ac24c85f9d8fc.view:
737 extents found
couchdb/.shards/80000000-9fffffff/foo2.1576202327_design/mrview/60c0365cb541a047d8841256fb5104af.view:
705 extents found
couchdb/.shards/80000000-9fffffff/foo2.1576202327_design/mrview/ff377ba3dcf6801401e64c4b47ee91f0.view:
704 extents found
couchdb/.shards/80000000-9fffffff/foo2.1576202327_design/mrview/54f171fe1f24ac4eb52ac24c85f9d8fc.view:
703 extents found
couchdb/.shards/20000000-3fffffff/foo2.1576202327_design/mrview/efaeb757cdb9120e0d2d312a237f955c.view:
41 extents found
couchdb/.shards/e0000000-ffffffff/foo2.1576202327_design/mrview/903132c98329dd5618a69593f92f1088.view:
34 extents found
couchdb/.shards/60000000-7fffffff/foo2.1576202327_design/mrview/efaeb757cdb9120e0d2d312a237f955c.view:
33 extents found
couchdb/shards/e0000000-ffffffff/demo.1576774963.couch: 32 extents found
couchdb/.shards/c0000000-dfffffff/foo2.1576202327_design/mrview/efaeb757cdb9120e0d2d312a237f955c.view:
32 extents found
couchdb/shards/c0000000-dfffffff/demo.1576774963.couch: 32 extents found
couchdb/shards/80000000-9fffffff/demo.1576774963.couch: 32 extents found
couchdb/shards/40000000-5fffffff/demo.1576774963.couch: 32 extents found
couchdb/shards/20000000-3fffffff/demo.1576774963.couch: 32 extents found
couchdb/shards/a0000000-bfffffff/demo.1576774963.couch: 31 extents found
couchdb/shards/60000000-7fffffff/demo.1576774963.couch: 31 extents found
couchdb/shards/00000000-1fffffff/demo.1576774963.couch: 31 extents found
couchdb/.shards/60000000-7fffffff/foo2.1576202327_design/mrview/77698c399d7c398c3fa2221d547b559a.view:
29 extents found
couchdb/.shards/e0000000-ffffffff/foo2.1576202327_design/mrview/77698c399d7c398c3fa2221d547b559a.view:
28 extents found
couchdb/shards/c0000000-dfffffff/_global_changes.1576197947.couch: 26
extents found
couchdb/.shards/00000000-1fffffff/foo2.1576202327_design/mrview/efaeb757cdb9120e0d2d312a237f955c.view:
26 extents found
couchdb/.shards/20000000-3fffffff/foo2.1576202327_design/mrview/903132c98329dd5618a69593f92f1088.view:
25 extents found
couchdb/.shards/80000000-9fffffff/foo2.1576202327_design/mrview/9e6552c45632f3e05a6ae72915e96b9b.view:
24 extents found
couchdb/.shards/c0000000-dfffffff/foo2.1576202327_design/mrview/54f171fe1f24ac4eb52ac24c85f9d8fc.view:
23 extents found
couchdb/.shards/a0000000-bfffffff/foo2.1576202327_design/mrview/1f3dc3019c5156f2aa66ab47248add61.view:
22 extents found
couchdb/.shards/80000000-9fffffff/foo2.1576202327_design/mrview/efaeb757cdb9120e0d2d312a237f955c.view:
21 extents found
couchdb/.shards/80000000-9fffffff/foo2.1576202327_design/mrview/1f3dc3019c5156f2aa66ab47248add61.view:
21 extents found
couchdb/.shards/00000000-1fffffff/foo2.1576202327_design/mrview/1f3dc3019c5156f2aa66ab47248add61.view:
21 extents found
couchdb/.shards/e0000000-ffffffff/foo2.1576202327_design/mrview/efaeb757cdb9120e0d2d312a237f955c.view:
19 extents found
couchdb/.shards/e0000000-ffffffff/foo2.1576202327_design/mrview/1f3dc3019c5156f2aa66ab47248add61.view:
19 extents found
couchdb/.shards/a0000000-bfffffff/foo2.1576202327_design/mrview/903132c98329dd5618a69593f92f1088.view:
19 extents found
couchdb/.shards/40000000-5fffffff/foo2.1576202327_design/mrview/9e6552c45632f3e05a6ae72915e96b9b.view:
19 extents found
couchdb/.shards/40000000-5fffffff/foo2.1576202327_design/mrview/37b94f6b5836a143c9db7b8a9caf45b9.view:
19 extents found
couchdb/.shards/80000000-9fffffff/foo2.1576202327_design/mrview/37b94f6b5836a143c9db7b8a9caf45b9.view:
18 extents found
couchdb/.shards/e0000000-ffffffff/foo2.1576202327_design/mrview/9e6552c45632f3e05a6ae72915e96b9b.view:
15 extents found
couchdb/.shards/a0000000-bfffffff/foo2.1576202327_design/mrview/37b94f6b5836a143c9db7b8a9caf45b9.view:
15 extents found
couchdb/.shards/40000000-5fffffff/foo2.1576202327_design/mrview/77698c399d7c398c3fa2221d547b559a.view:
15 extents found
couchdb/.shards/60000000-7fffffff/foo2.1576202327_design/mrview/9e6552c45632f3e05a6ae72915e96b9b.view:
14 extents found
couchdb/.shards/20000000-3fffffff/foo2.1576202327_design/mrview/37b94f6b5836a143c9db7b8a9caf45b9.view:
13 extents found
couchdb/.shards/c0000000-dfffffff/foo2.1576202327_design/mrview/1f3dc3019c5156f2aa66ab47248add61.view:
12 extents found
couchdb/.shards/60000000-7fffffff/foo2.1576202327_design/mrview/37b94f6b5836a143c9db7b8a9caf45b9.view:
12 extents found
couchdb/.shards/a0000000-bfffffff/foo2.1576202327_design/mrview/efaeb757cdb9120e0d2d312a237f955c.view:
9 extents found
couchdb/.shards/80000000-9fffffff/foo2.1576202327_design/mrview/77698c399d7c398c3fa2221d547b559a.view:
9 extents found
couchdb/.shards/e0000000-ffffffff/foo2.1576202327_design/mrview/37b94f6b5836a143c9db7b8a9caf45b9.view:
8 extents found
couchdb/.shards/80000000-9fffffff/foo2.1576202327_design/mrview/903132c98329dd5618a69593f92f1088.view:
8 extents found
couchdb/.shards/60000000-7fffffff/foo2.1576202327_design/mrview/1f3dc3019c5156f2aa66ab47248add61.view:
8 extents found
couchdb/.shards/20000000-3fffffff/foo2.1576202327_design/mrview/77698c399d7c398c3fa2221d547b559a.view:
8 extents found
couchdb/.shards/00000000-1fffffff/foo2.1576202327_design/mrview/903132c98329dd5618a69593f92f1088.view:
8 extents found
couchdb/.shards/40000000-5fffffff/foo2.1576202327_design/mrview/54f171fe1f24ac4eb52ac24c85f9d8fc.view:
7 extents found
couchdb/.shards/40000000-5fffffff/foo2.1576202327_design/mrview/903132c98329dd5618a69593f92f1088.view:
6 extents found
couchdb/.shards/00000000-1fffffff/foo2.1576202327_design/mrview/9e6552c45632f3e05a6ae72915e96b9b.view:
6 extents found
couchdb/shards/e0000000-ffffffff/_global_changes.1576197947.couch: 5 extents
found
couchdb/.shards/a0000000-bfffffff/foo2.1576202327_design/mrview/9e6552c45632f3e05a6ae72915e96b9b.view:
5 extents found
couchdb/.shards/c0000000-dfffffff/foo2.1576202327_design/mrview/9e6552c45632f3e05a6ae72915e96b9b.view:
4 extents found
couchdb/.shards/c0000000-dfffffff/foo2.1576202327_design/mrview/37b94f6b5836a143c9db7b8a9caf45b9.view:
4 extents found
couchdb/.shards/60000000-7fffffff/foo2.1576202327_design/mrview/903132c98329dd5618a69593f92f1088.view:
4 extents found
couchdb/.shards/40000000-5fffffff/foo2.1576202327_design/mrview/efaeb757cdb9120e0d2d312a237f955c.view:
4 extents found
couchdb/.shards/40000000-5fffffff/foo2.1576202327_design/mrview/1f3dc3019c5156f2aa66ab47248add61.view:
4 extents found
couchdb/.shards/20000000-3fffffff/foo2.1576202327_design/mrview/9e6552c45632f3e05a6ae72915e96b9b.view:
4 extents found
couchdb/.shards/20000000-3fffffff/foo2.1576202327_design/mrview/1f3dc3019c5156f2aa66ab47248add61.view:
4 extents found
couchdb/shards/60000000-7fffffff/_global_changes.1576197947.couch: 3 extents
found
couchdb/.shards/00000000-1fffffff/foo2.1576202327_design/mrview/77698c399d7c398c3fa2221d547b559a.view:
3 extents found
couchdb/_dbs.couch: 3 extents found
couchdb/.shards/c0000000-dfffffff/foo2.1576202327_design/mrview/77698c399d7c398c3fa2221d547b559a.view:
2 extents found
couchdb/.shards/a0000000-bfffffff/foo2.1576202327_design/mrview/77698c399d7c398c3fa2221d547b559a.view:
2 extents found
couchdb/shards/80000000-9fffffff/_global_changes.1576197947.couch: 2 extents
found
couchdb/shards/20000000-3fffffff/_global_changes.1576197947.couch: 2 extents
found
couchdb/shards/00000000-1fffffff/_users.1576197947.couch: 2 extents found
couchdb/.shards/00000000-1fffffff/foo2.1576202327_design/mrview/37b94f6b5836a143c9db7b8a9caf45b9.view:
2 extents found
couchdb/._users_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view: 1
extent found
couchdb/_users.couch: 1 extent found
couchdb/.shards/e0000000-ffffffff/_users.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/shards/e0000000-ffffffff/_users.1576197947.couch: 1 extent found
couchdb/.shards/e0000000-ffffffff/_replicator.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/shards/e0000000-ffffffff/_replicator.1576197947.couch: 1 extent found
couchdb/.shards/e0000000-ffffffff/demo.1576774963_design/mrview/c12a4679354f40965b2fac59260bad86.view:
1 extent found
couchdb/.shards/c0000000-dfffffff/_users.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/shards/c0000000-dfffffff/_users.1576197947.couch: 1 extent found
couchdb/.shards/c0000000-dfffffff/foo2.1576202327_design/mrview/903132c98329dd5618a69593f92f1088.view:
1 extent found
couchdb/.shards/c0000000-dfffffff/_replicator.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/shards/c0000000-dfffffff/_replicator.1576197947.couch: 1 extent found
couchdb/.shards/c0000000-dfffffff/demo.1576774963_design/mrview/c12a4679354f40965b2fac59260bad86.view:
1 extent found
couchdb/.shards/a0000000-bfffffff/_users.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/shards/a0000000-bfffffff/_users.1576197947.couch: 1 extent found
couchdb/.shards/a0000000-bfffffff/_replicator.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/shards/a0000000-bfffffff/_replicator.1576197947.couch: 1 extent found
couchdb/shards/a0000000-bfffffff/_global_changes.1576197947.couch: 1 extent
found
couchdb/.shards/a0000000-bfffffff/demo.1576774963_design/mrview/c12a4679354f40965b2fac59260bad86.view:
1 extent found
couchdb/.shards/80000000-9fffffff/_users.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/shards/80000000-9fffffff/_users.1576197947.couch: 1 extent found
couchdb/.shards/80000000-9fffffff/_replicator.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/shards/80000000-9fffffff/_replicator.1576197947.couch: 1 extent found
couchdb/.shards/80000000-9fffffff/demo.1576774963_design/mrview/c12a4679354f40965b2fac59260bad86.view:
1 extent found
couchdb/.shards/60000000-7fffffff/_users.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/shards/60000000-7fffffff/_users.1576197947.couch: 1 extent found
couchdb/.shards/60000000-7fffffff/_replicator.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/shards/60000000-7fffffff/_replicator.1576197947.couch: 1 extent found
couchdb/.shards/60000000-7fffffff/demo.1576774963_design/mrview/c12a4679354f40965b2fac59260bad86.view:
1 extent found
couchdb/.shards/40000000-5fffffff/_users.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/shards/40000000-5fffffff/_users.1576197947.couch: 1 extent found
couchdb/.shards/40000000-5fffffff/_replicator.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/shards/40000000-5fffffff/_replicator.1576197947.couch: 1 extent found
couchdb/shards/40000000-5fffffff/_global_changes.1576197947.couch: 1 extent
found
couchdb/.shards/40000000-5fffffff/demo.1576774963_design/mrview/c12a4679354f40965b2fac59260bad86.view:
1 extent found
couchdb/.shards/20000000-3fffffff/_users.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/shards/20000000-3fffffff/_users.1576197947.couch: 1 extent found
couchdb/.shards/20000000-3fffffff/_replicator.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/shards/20000000-3fffffff/_replicator.1576197947.couch: 1 extent found
couchdb/.shards/20000000-3fffffff/demo.1576774963_design/mrview/c12a4679354f40965b2fac59260bad86.view:
1 extent found
couchdb/.shards/00000000-1fffffff/_users.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/.shards/00000000-1fffffff/_replicator.1576197947_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view:
1 extent found
couchdb/shards/00000000-1fffffff/_replicator.1576197947.couch: 1 extent found
couchdb/shards/00000000-1fffffff/_global_changes.1576197947.couch: 1 extent
found
couchdb/.shards/00000000-1fffffff/demo.1576774963_design/mrview/c12a4679354f40965b2fac59260bad86.view:
1 extent found
couchdb/._replicator_design/mrview/3e823c2a4383ac0c18d4e574135a5b08.view: 1
extent found
couchdb/_replicator.couch: 1 extent found
couchdb/_nodes.couch: 1 extent found
```
How should we interpret those results?
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