Understanding RAM Disk Path setting

You may experience high I/O load issue on your server and wondering if RAM Disk Path (setting under configuration→server→tuning→RAM Disk Path. ) would help and what kind of data will be stored to RAM Disk if it is set. Actually this setting is only for LSWS real time stats data, not for swapping directory or anything else. Mitigation to your server high I/O issue may be very limited.

General speaking, swap directory can be set to your RAM disk. PHP session path can also be set to RAM disk. These can be set explicitly through the dedicate configuration instead of from LSWS. However, you can set GZIP Compression Static GZIP Cache Directory in LSWS to RAM disk if you like.

Overall LSWS has been optimized for most of the scenarios. Occasionally, if your server is constantly dealing with dynamic content with request/response body larger than 1MB, LSWS may use temporary file to store the body data, which could increase disk I/O activities and cause higher I/O wait. However, it rarely happens.

Higher I/O wait is normally caused by higher disk I/O activities. There could be caused by many factors. Good practice is to identify where the disk I/O activities coming from instead of setting everything above without knowing the root cause. You may run iotop command to find out more, or do some strace on the process which generates a lot of disk I/O. Once root cause identified, RAM disk may help, though, the setting could be on your OS level instead of LiteSpeed Web Server level.