On Tue, 24 Jan 2006, Kai Makisara wrote:
Put
options st try_direct_io=0
in /etc/modprobe.conf. Direct I/O defeats read-ahead, and
significantly (factor of >5) degrates read performance. I don't know
about writes.
The only thing that could be seen in Gerhard's tests with try_direct_io=0
should be higher CPU load. It probably won't have any effect on the speed
in these tests.
I will let Gerhard speak for himself, but it made an enormous
difference in our tests. The buffer size in the tape device is 64K,
matching the read-ahead to that buffer size gave maximum performance.
Chip
--
Charles M. "Chip" Coldwell
Senior Software Engineer
Red Hat, Inc
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