...

These are ballpark numbers, and your millage will vary enormously. JPEG for example will not compress with any of these. The RamCache does detect compression level and will declare something "incompressible" if it doesn't get below 90% of the original size. This value is cached so that the RamCache will not attempt to compress it again (at least as long as it is in the history).

ram cache and memory issues and roadmap

• how to control the memory usage by hostname etc
• can we use share memory to host ram cache? which will help us get high memory hit ratio even after a restart
• can we unbind the ram cache and vol? which may make ram cache a better performance and easy to use, for example in ET_CLUSTER we can read from ram cache directly if hit, otherwise we can shcedule an cache read.
• can we setup an ram cache space for origin side cache before it is synced to disk, and we can set for better checking for example we can track xxM objects in 2G ram, and only write to disk when that object is hit by 2 times.