For more information, you can also refer to "Disk Cache Settings and Recommend" in CCBoot v3.0 Wiki.

Recommended Server Settings

Server Physical RAM	Image Cache	Game Cache	Write-back Cache
2G	256M	512M	256M
4G	512M	1024M	1024M
8G	1024M	4096M	2048M
16G	1024M	10240M	4096M
32G	1024M	20480M	10240M

Recommended Client Cache Settings

Client Physical RAM	Image Disk Cache
1G	256M
2G	384M
4G	512M

For more details about cache settings, please refer to this article.