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IIS supports different log file formats; its own Microsoft IIS log file format, the NCSA Common and the W3C Extended log file formats. The W3C extended log file format is the most versatile as it offers customizable output to accommodate individual needs.
Forsta recommends setting up IIS to store log files on a different partition than the operating system or setting up a log file archival process if possible to avoid disk space problems if the logs outgrow the available partition space.
IIS Log File Archiving
Web server and SMTP logs can grow substantially in size on busy systems. Two easy ways of controlling log size are by enabling NTFS compression on the log directory and archiving logs.
Enabling NTFS compression on the log directory will reduce the physical space required to store logs, but can add some overhead to the I/O performance on the system, specifically on very busy servers.
Archiving logs for external storage is a more performance/cost effective solution and can be customized to accommodate most needs. Log archiving can be set up as a scheduled task on the servers.