BlueCielo Meridian Enterprise 2016 Administrator's Guide

Understanding BlueCielo SQLIO

BlueCielo SQLIO (not to be confused with Microsoft SQLIO) is a SQL Server-specific component that interfaces between the Meridian object cache and SQL Server. Every data change inside Meridian needs to be committed to the SQL Server database as soon as possible. Due to loads that may be placed on SQL Server by other applications and latency induced by the network between the Meridian application server and the SQL Server computer, it can take a significant amount of time for SQL Server to commit data changes, which can lead to poor performance. To avoid this bottleneck, BlueCielo SQLIO uses a write-ahead log mechanism illustrated in the figure in the section Understanding how Meridian works with SQL Server.

Instead of directly committing data to SQL Server, BlueCielo SQLIO’s main thread commits data to log files (not to be confused with the SQL Server database log) stored on the Meridian application server. At this point, the data is considered by Meridian as committed and it can continue its work and the user will experience good responsiveness. A second thread in BlueCielo SQLIO reads the log files and updates the SQL Server database.

The write-ahead log mechanism maintains the integrity of the data. For example, when data needs to be retrieved by the Meridian application server, it requests the data from the object cache. If the data is not cached, it requests the data from BlueCielo SQLIO, which first checks whether this data is in the write-ahead log, and only if it is not found does BlueCielo SQLIO request the data from SQL Server.

If a lot of data is changed over a sustained period of time (for example, as the result of a batch import), the number of BlueCielo SQLIO log files will grow because they cannot be processed by SQL Server as fast as they are created by the BlueCielo SQLIO driver. This does not have a detrimental effect on the system performance, but the disk could run out of space if the number of log files keeps growing indefinitely. The maximum amount of space used for all log files can be configured as described in Configuring the MaximumLogSize setting.Understanding the effects of the CPU

SQL Server stops processing the BlueCielo SQLIO log files when the vault is closed, that is, after the last client closes its connection to the server. Log files that have not been processed by that time will remain until the vault is reopened and the processing starts again. This is not a serious performance issue because Meridian allows for vaults to become available immediately after reopening them; users do not have to wait for the existing log files to be processed.

BlueCielo SQLIO uses a service account to communicate with SQL Server. Regardless of the number of users of the system, it takes up only one connection to the database.