Kbase 14164: -directio on Sequent PTX
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
10/05/1998 |
|
-directio on Sequent PTX
As with many things that have to do with performance,
"Your mileage may vary".
What direct i/o on Sequent PTX does is very similar to using
raw partitions. Using direct i/o means that all database reads
and write bypass the PTX buffer pool. The data transfers go straight
from the Progress database buffer pool to the disk controller.
This has two benefits: there is less overhead because the data are
not copied to and from the kernel's buffers, and the transfers are the
same size as the database buffers instead of the filesystem page size.
On the other hand, there are drawbacks: there may be less total
buffering because the data are not buffered in the PTX buffer pool,
only in the Progress buffer pool, you lose the potential benefit of
any PTX read-ahead that might occur, and the total number of disk
transfers *may* be greater.
Using -directio on Sequent PTX can result in a 30% performance gain.
Whether -directio helps or not depends a lot on what the application
does and how it does it, so it is difficult for to estimate how it
will behave on your system. Certainly not every app will see 30%
performance gain. There may be a net loss.
Progress Software Technical Support Note # 14164