Analysis to determine what to place on SSD
files falls under two categories, operating system level analysis
and Oracle internal analysis. Both methods involve analyzing the
I/O wait interface from either the system or Oracle perspective.
In many situations, the operating system level
analysis may be inconclusive due to the combining of physical
disks into large, RAID combined logical disks. In this case, the
I/O to the individual datafiles from the Oracle perspective must
get a good look.
Inside Oracle, there are two areas to look at
to determine the best candidates for placement on the SSD asset.
These two are the I/O statistics and the wait interface
statistics. Looking at the I/O interface for average I/O times and
total I/O to specific datafiles helps determine usage patterns for
datafiles and temp files. Looking at the wait interface helps
determine if processes are waiting on I/O related events and what
events are being waited on.
The analyst has several possible sources for
the I/O and wait interface statistics:
The use of custom scripts gives the analyst
control over the selection and display of specific statistics of
concern. Oracle Enterprise Manager (OEM)
provides a plethora of data but may not be available at all sites.
Third-party tools also provide a wealth of data but are expensive
and may not be installed at all client locations. STATSPACK
reports are available at all sites, provide a wealth of statistics
and allow a focused look at specific time intervals.
Of the available data gathering methods,
scripts and STATSPACKwill be
the focus in this chapter.