Questions
This section discusses some of the common questions about XIO.
Question Answer
Can I use XIO in a clustering environment?
No. Xtreme I/O must not be installed if Pervasive PSQL is being used in a clustering environment. A node with XIO installed can hang when the machine comes online through a failover and leave the shared storage inaccessible.
Therefore, on the installation Setup Type dialog for Pervasive PSQL, select Custom. If “Pervasive Xtreme I/O” displays as an available installation option, click that option. Select “This feature will not be available.”
Complete the rest of the Pervasive PSQL installation. No further customizing is required.
Can I use XIO on a Virtual Machine? No. Xtreme I/O must not be installed if Pervasive PSQL is being used on a Virtual Machine.
Is XIO included with Pervasive PSQL Vx Server?
No. Although Pervasive PSQL Vx Server Vx can be installed on a physical machine, it is primarily intended for virtual environments. Since XIO must not be used in virtual environments it is not included as part of the Pervasive PSQL Vx Server installation. How do I know if XIO is installed? Check for the XIO message in the pvsw.log file. See Pvsw.log
Message.
Or, at a command prompt, execute the command xiomgr. If the operating system reports the help information for xiomgr, then the XIO driver is installed.
How do I know if XIO is enabled? Run the utility xiomgr with the “query” option: xiomgr -query. The utility reports the current state of XIO (enabled or disabled) How do I know if XIO is running?
Utilities
XIO provides two utilities for working with the driver: xiomgr and xiostats.Xiomgr
Availability How do I know how efficient the XIO cache is?
In general, check the percentage for the “Read Hit %” statistic. The larger the percentages, the more that the XIO cache is being used, and the more efficiently XIO increases performance.
To a lesser extent, you can also check the “Cacheable IO %” statistic, which indicates the percentage of all I/O requests that pertain exclusively to Pervasive PSQL data. A high percentage indicates that the majority of disk access requests involve Pervasive PSQL data.
See also Xiostats Statistics. How do I know what files are cached in
the XIO cache?
Run the utility Xiostats. Click View then Open Files. See also Tour of Features.
Why does the “Open Cached Files” statistic show more or fewer files than the number of files I think I have open?
The database engine may open a file and then close it, in which case it will not be counted among the open cached files. Opening a segmented Pervasive PSQL of four segments indicates that four files are open, not just one. The database engine performs a file open operation for each segment. System files, System files and data dictionary files may also be open, which are included in the total.
See also Xiostats Statistics.
Question Answer
Xtreme I/O Driver
Options
Xiostats
This utility displays statistical information about the XIO cache. Note that Xiostats is primarily an advanced utility intended for users who have a thorough understanding of statistics and viewing
-query Report the current state of the XIO driver, such as whether or not it is running or enabled.
-start Start the XIO driver.
If issued following an xiomgr -stop command, ensure that the database engine services are started first. See also Troubleshooting XIO.
-stop Stop the XIO driver.
The database engine services must be stopped first. See also
Troubleshooting XIO.
-enable Start the XIO driver when the operating system starts.
The enable option takes effect the next time you boot the operating system.
-disable Prevent the XIO driver from starting when the operating system starts. The disable option takes effect the next time you boot the operating system.
in the main window of the utility. The following table explains the statistics.
Table 22 Xiostats Statistics
Statistic Meaning
Time The system date and time.
Elapsed Seconds The number of seconds elapsed since Xiostats was invoked. That is, how long in seconds it has been running. Physical Memory The approximate total physical memory, including
extended memory, on the machine.
Cache Size The size of the XIO cache in megabytes. This value can vary depending on which memory the cache is using. See
Memory Usage.
Open Cached Files The number of Pervasive PSQL files open and actively being cached (the file is being read from or written to). Note that the total number of opened cached files may differ from the number you think are open. Opening a file may result in multiple physical files being opened. For example, a segmented Pervasive PSQL of four segments indicates that four files are open, not just one. The database engine performs a file open operation for each segment.
Compression Ratio The amount of data compression performed by the cache.
For example, suppose that the Compression Ratio is 8 (meaning 8 to 1). If your cache is 1 GB in size and your compression ration is 8, the cache is storing 8 GB of data. This ratio depends on the characteristics of the data. Some data can be compressed, other data cannot. Read Hit % “Hit” refers to XIO reading the data from its cache not from
Xtreme I/O Driver
Cacheable IO % The percentage of all I/O requests that pertain exclusively to Pervasive PSQL data. (XIO is aware of all disk access requests but acts only on those pertaining to Pervasive PSQL data.)
If your server is dedicated exclusively to Pervasive PSQL, Cacheable IO % should show a high percentage because the majority of disk access requests involve Pervasive PSQL data.
Cache Read Bytes The number of bytes read from the cache. Cache Write Bytes The number of bytes written to the cache.
Table 22 Xiostats Statistics
Tour of Features
The following table provides a brief tour of the utility features that support the statistical reporting.
Feature Description
Options The Options dialog lets you customize certain aspects of the utility, such as the interval in which Xiostats polls its cache. The
Options command is accessed from the File menu. Parameters The Parameters list shows you the various Registry settings
for Xiostats. You can customize only two of the settings. See
Registry Settings.
Do not modify any XIO registry entries except the two listed under Registry Settings. Unpredictable results can occur. The Parameters command is accessed from the View menu. Opened Files The Opened Files list is useful to view which files are currently
opened and cached.
The Opened Files command is accessed from the View
menu.
PerfMon The PerfMon command provides a convenient way to access the counters for the PerfMon utility. The PerfMon utility is included as part of the Windows operating system. Refer to its documentation for the use of counters.
Graph The Graph command lets you graph the statistical data and view it different ways. You can view data by graphing the variable, derivative, or integral.
You can also graph statistical data that has been saved to an Xiostats log. An Xiostats log is a text file saved in comma separated value (csv) format that can be viewed in a spreadsheet program.
You open and close log files (csv files) with the commands in the File menu.
Xtreme I/O Driver
Exclusions File
XIO includes a text file, xioexclude.lst, that allows you to specify data files not to accelerate. Typically, you do not need to add exclusions. However, if you choose to exclude files, follow these steps:1 Open the file in a text editor.
By default, the file is located in Pervasive Software\PSQL under %allusersprofile%. Ensure that you search for hidden files because, by default, the operating system hides certain folders under %allusersprofile%.
2 Add file names by following the instructions in xioexclude.lst.
3 Reboot the operating system.