Here is some suggestions
Some are for future version cause it's my imagination of an absolute Fancycahe
---1- Deferred write feature : Add the possibility to choose the speed of writing at the end of set time
---2- Exclude directory list from Deferred write
---3- Feature to exclude System file from "Deferred write"
---4- Flush cache to disk on system error (blue screen) like windows do (not easy to do i know)
------and may be finish the cache cleaning on reboot or ask the user or add an option on windows boot menu...
---5- Let the user choose what to cache :
------5a- Possibility of disabling cache algorithm and let the user choose what to cache
------5b- Plus/Less the incorporated algorithm, let the user add a list (directory/application) ...
------(if directory it's simple and if it's application fancy cache must take automatically needed dlls)
------5c- Plus/Less the incorporated algorithm, add a form with check box where you list predefined think to cache
------(example : ¤ System file ¤ Boot File ¤ Shared DLLs ¤ Explorer and her stuff ¤ Internet Softs ¤ PageFile)
---6- Feature to write deferred cache when disk is idle
---7- Exclude list (directory excluded from cache) ... (told it in an other place of the forum)
---8- Gamers mode... (where we could choose a game and fancycache will concentrate only on this apps)
---9- Tray Icon : add a tray icon of fancy cache like that we could use the options/Action and modifications easily
------9a- Lunching performance monitor on right click
------9b- Disabling tray icon without stopping the soft (kill the exe keeping the driver)
------9c- Execute deferred write
------9d- Enable/disable on boot Tray icon
------9e- Check Disk : Check the disk to see if there is file/index error
---10- A tool to view cache content and the possibility to discard selected item from the list (a little like taskmgr)
---11- An energy saver mode (for laptop for example) when activated use less cpu and reduce hard disk write speed
------and maybe use more time for differed write
---12- Use a ramdisk or an other place to store the cache (you could check the speed of added place to notify the user
------if it's recommended or not) about ram disk it will be cool cose it add all feature of ramdisk to fancycache like mirror saving etc.
---13- Execute deferred write on "Stop" button (i don't know if you implement it or not)
---14- Can i integrate the development team ? looooooooooooool

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Will posts others when i find... hope it's helping you (and not retarding the development it's why i indicated some is for future)