From c343c3f7f6aea23bb439a6500166673c4b1e6f2c Mon Sep 17 00:00:00 2001 From: Dominik Csapak Date: Tue, 7 May 2024 15:45:52 +0200 Subject: [PATCH] tape: improve throughput by not unnecessarily syncing/committing When writing data on tape, the idea was to sync/committing to tape and the catalog to disk every 128GiB of data. For that the counter 'bytes_written' was introduced and checked after every chunk/snapshot archive. Sadly we forgot to reset the counter after doing so, which meant that after 128GiB was written onto the tape, we synced/committed after every archive on the tape for the remaining length of the tape. Since syncing to tape and writing to disk takes a bit of time, the drive had to slow down every time and reduced the available throughput. (In our tests here from ~300MB/s to ~255MB/s). By resetting the value to zero after syncing, we avoid that and increase throughput performance when backups are bigger than 128GiB on tape. Signed-off-by: Dominik Csapak --- src/tape/pool_writer/mod.rs | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/src/tape/pool_writer/mod.rs b/src/tape/pool_writer/mod.rs index 214260804..1a47e837c 100644 --- a/src/tape/pool_writer/mod.rs +++ b/src/tape/pool_writer/mod.rs @@ -43,7 +43,7 @@ struct PoolWriterState { media_uuid: Uuid, // tell if we already moved to EOM at_eom: bool, - // bytes written after the last tape fush/sync + // bytes written after the last tape flush/sync and catalog commit bytes_written: usize, } @@ -200,8 +200,9 @@ impl PoolWriter { /// This is done automatically during a backupsession, but needs to /// be called explicitly before dropping the PoolWriter pub fn commit(&mut self) -> Result<(), Error> { - if let Some(PoolWriterState { ref mut drive, .. }) = self.status { - drive.sync()?; // sync all data to the tape + if let Some(ref mut status) = self.status { + status.drive.sync()?; // sync all data to the tape + status.bytes_written = 0; // reset bytes written } self.catalog_set.lock().unwrap().commit()?; // then commit the catalog Ok(())