The Storage I/O feature in DPA frequently collects file statistics from a monitored database instance. If the instance includes a large number of files, collecting I/O data can incur excessive overhead for both the monitored instance and for DPA. To avoid performance issues, DPA automatically disables storage I/O polling when the number of files exceeds a specified limit. The default limit is 250.
If storage I/O polling is disabled, you will see a message similar to the one below when you attempt to access Storage I/O:
Storage I/O has been automatically disabled for this database instance due to the large number of files in this database instance. This was done because gathering I/O data for a large number of files may negatively affect the performance of both DPA and the database instance.
353 files detected. Current limit is 250.
Additionally, the idc.log includes a log entry similar to the one below:
IOCollectionServiceImpl - Disabling IO stats collection for database [id=3] because the number of files 315 exceeds the IO stats poll file limit.
If you choose to re-enable storage I/O polling for a database instance with a large number of files, be aware of the following options and their effect on performance.
Determines whether storage I/O polling is enabled, and whether this value automatically changes based on the file limit. The following values are available:
If you see the error described in the previous section, DPA has changed this option to AUTO_OFF.
Specifies the maximum number of files that can reside on a database instance before DPA automatically disables storage I/O polling. Applies only if the enablement mode is AUTO_ON or AUTO_OFF.
Specifies how often storage I/O data is collected. Polling too frequently with a large number of files can negatively affect performance.
To re-enable storage I/O polling for a monitored instance with a large number of files, complete the following steps to increase the file limit and (if necessary) decrease the polling frequency.
Note: Alternatively, you can tell DPA to ignore the file limit and always enable storage I/O polling. To do so, set IO_STATS_POLL_ENABLED (on the DB Instance Options tab) to MANUAL_ON. However, be aware that MANUAL_ON is not recommended because it can negatively affect performance.
We recommend that you follow these instructions under the guidance of SolarWinds Support.
IOCollectionServiceImpl - Error collecting IO Stats for QASQL2K12. IO Stat collection for this entity will be retried in 5 minutes. Retries will continue indefinitely, however, this error will only be logged after every 10th failed attempt. This error can be ignored if sporadic.
IOCollectionServiceImpl - IO Stats query gap detected for dbId  last collection: 03/14/2015 08:55:11, current collection: 03/14/2015 08:56:31, difference  > 30000
IOCollectionServiceImpl - Added file to blacklist [dbId:35] [dbId=2, fileId=5 [2|5]] [expires: 03/16/2015 12:05:30] Missing stats detected.