diff options
Diffstat (limited to 'Documentation/public-inbox-tuning.pod')
| -rw-r--r-- | Documentation/public-inbox-tuning.pod | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/Documentation/public-inbox-tuning.pod b/Documentation/public-inbox-tuning.pod index abc53d1e..e3f2899b 100644 --- a/Documentation/public-inbox-tuning.pod +++ b/Documentation/public-inbox-tuning.pod @@ -69,7 +69,8 @@ footprint when indexing on HDDs. Initializing a mirror with a high C<--jobs> count to create more shards (in C<-V2> inboxes) will keep each shard smaller and -reduce its kernel page cache footprint. +reduce its kernel page cache footprint. Keep in mind excessive +sharding imposes a performance penalty for read-only queries. Users with large amounts of RAM are advised to set a large value for C<publicinbox.indexBatchSize> as documented in @@ -88,12 +89,21 @@ used by public-inbox are no exception to that. public-inbox 1.6.0+ disables copy-on-write (CoW) on Xapian and SQLite indices on btrfs to achieve acceptable performance (even on SSD). -Disabling copy-on-write also disables checksumming, thus raid1 -(or higher) configurations may corrupt on unsafe shutdowns. +Disabling copy-on-write also disables checksumming, thus C<raid1> +(or higher) configurations may be corrupt after unsafe shutdowns. Fortunately, these SQLite and Xapian indices are designed to recoverable from git if missing. +Disabling CoW does not prevent all fragmentation. + +Avoid snapshotting subvolumes containing Xapian and/or SQLite indices. +Snapshots use CoW despite our efforts to disable it, resulting +in fragmentation. + +L<filefrag(8)> can be used to monitor fragmentation, and +C<btrfs filesystem defragment -fr $INBOX_DIR> may be necessary. + Large filesystems benefit significantly from the C<space_cache=v2> mount option documented in L<btrfs(5)>. @@ -106,6 +116,11 @@ While SSD read performance is generally good, SSD write performance degrades as the drive ages and/or gets full. Issuing C<TRIM> commands via L<fstrim(8)> or similar is required to sustain write performance. +Users of the Flash-Friendly File System +L<F2FS|https://en.wikipedia.org/wiki/F2FS> may benefit from +optimizations found in SQLite 3.21.0+. Benchmarks are greatly +appreciated. + =head2 Read-only daemons L<public-inbox-httpd(1)>, L<public-inbox-imapd(1)>, and |