The Volera Excelerator appliance provides a high-performance proxy cache system capable of handling thousands of transactions per second. Even though Excelerator can log extensive details of each transaction and the disk space reserved for log files is quite generous on most appliances, Excelerator can fill up the available disk space in a matter of minutes if transaction volume is high and log entries consume a few hundred bytes each.
This section explains how appliance logging works and presents management options you can use to ensure optimal use of the available log file disk space and timely migration (downloading) of log files to other storage devices.
The following table shows the transactions the appliance can log and the formats available for each service type.
Turning on logging for a given service increases system overhead and causes some performance degradation. Therefore, logging should be used only when service transactions must be tracked for customer billing purposes or other compelling reasons.
Transaction volume and log entry size can cause available log disk space to fill up quickly. Proxy cache disk space is unaffected by log files.
See Planning Step 3: Calculating Log Rollover Requirements for formulas you can use to estimate how quickly your logging disk will fill.
To plan a logging strategy, you must know the capacity and limitations of your appliance.
It is essential that you know how much logging disk space is available on your appliance.
Logging disk space is not user-configurable; it is preset by the vendor who produced your appliance. Most vendors allocate different amounts of disk space for log files on each level or tier of appliance they produce.
If you don't have this information, you must get it from your appliance vendor before you can plan a logging strategy. After you determine how much disk space is available, you can plan when to download and delete log files so the disk does not become full.
Excelerator will not allow the deletion of active log files---files that are currently in use by the caching system. Only log files that have been rolled over and closed can be deleted.
You can ensure you have closed files on the system by scheduling regular rolling over of log files. During each rollover, the current log file is closed and a new log file is opened.
You must plan your log file rollover schedule to coincide with your download and deletion schedule so that you have at least one closed log file per service when the download and delete cycle starts.
NOTE: Although you can download active log files, this is normally useful only for periodic administrative checks.
Active files contain only the transaction data up to the moment of the download and are incomplete from customer billing and other business standpoints.
When the appliance encounters a log disk full condition, it stops logging and closes all active log files. Information that would have been logged after that point is lost. Other appliance functions continue without interruption.
The appliance automatically generates log filenames as follows:
NOTE: The dash is not included after the letters double.
This naming convention accommodates up to 702 log files per service per day. If the rollover options are set so that all the possible filenames are used in one day, the log file with the ZZ letter identifier is not closed until the start of the next day (unless the logging disk becomes full).
Appliance log rollover options let you specify when the appliance closes active log files and opens new files so that the closed files can be downloaded and deleted.
Because of the limitations explained in this section, it is essential that you develop a solid log file rollover plan. This will ensure that your appliance doesn't run out of logging disk space or overwrite log files before they are downloaded and deleted.
You can have the appliance roll log files over according to time or file size, as explained in the following table: