|author||Kai Makisara <Kai.Makisara@kolumbus.fi>||2010-10-09 00:17:56 +0300|
|committer||James Bottomley <James.Bottomley@suse.de>||2010-10-08 17:16:22 -0500|
[SCSI] st: add MTWEOFI to write filemarks without flushing drive buffer
This patch adds a new MTIOCTOP operation MTWEOFI that writes filemarks with immediate bit set. This means that the drive does not flush its buffer and the next file can be started immediately. This speeds up writing in applications that have to write multiple small files. Signed-off-by: Kai Makisara <email@example.com> Signed-off-by: James Bottomley <James.Bottomley@suse.de>
Diffstat (limited to 'Documentation/scsi')
1 files changed, 14 insertions, 1 deletions
diff --git a/Documentation/scsi/st.txt b/Documentation/scsi/st.txt
index 40752602c05..691ca292c24 100644
@@ -2,7 +2,7 @@ This file contains brief information about the SCSI tape driver.
The driver is currently maintained by Kai Mäkisara (email
-Last modified: Sun Feb 24 21:59:07 2008 by kai.makisara
+Last modified: Sun Aug 29 18:25:47 2010 by kai.makisara
@@ -85,6 +85,17 @@ writing and the last operation has been a write. Two filemarks can be
optionally written. In both cases end of data is signified by
returning zero bytes for two consecutive reads.
+Writing filemarks without the immediate bit set in the SCSI command block acts
+as a synchronization point, i.e., all remaining data form the drive buffers is
+written to tape before the command returns. This makes sure that write errors
+are caught at that point, but this takes time. In some applications, several
+consecutive files must be written fast. The MTWEOFI operation can be used to
+write the filemarks without flushing the drive buffer. Writing filemark at
+close() is always flushing the drive buffers. However, if the previous
+operation is MTWEOFI, close() does not write a filemark. This can be used if
+the program wants to close/open the tape device between files and wants to
If rewind, offline, bsf, or seek is done and previous tape operation was
write, a filemark is written before moving tape.
@@ -301,6 +312,8 @@ MTBSR Space backward over count records.
MTFSS Space forward over count setmarks.
MTBSS Space backward over count setmarks.
MTWEOF Write count filemarks.
+MTWEOFI Write count filemarks with immediate bit set (i.e., does not
+ wait until data is on tape)
MTWSM Write count setmarks.
MTREW Rewind tape.
MTOFFL Set device off line (often rewind plus eject).