From: Dominik Csapak <d.csapak@proxmox.com>
To: pbs-devel@lists.proxmox.com
Subject: [pbs-devel] [PATCH proxmox-backup 1/2] tape: improve throughput by not unnecessarily syncing/committing
Date: Tue, 7 May 2024 15:45:52 +0200 [thread overview]
Message-ID: <20240507134553.3233550-1-d.csapak@proxmox.com> (raw)
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 <d.csapak@proxmox.com>
---
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(())
--
2.39.2
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next reply other threads:[~2024-05-07 13:46 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-07 13:45 Dominik Csapak [this message]
2024-05-07 13:45 ` [pbs-devel] [PATCH proxmox-backup 2/2] examples: add tape write benchmark Dominik Csapak
2024-05-08 7:06 ` [pbs-devel] applied: [PATCH proxmox-backup 1/2] tape: improve throughput by not unnecessarily syncing/committing Dietmar Maurer
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