Deleting Files Doesn't Free Space in a Storage Pool

hello,

windows server 2012 essentials started complain storage pool low on capacity, of physical disks @ 71%.  instead of adding 2 more disks mirrored pool, created new mirrored pool and, through dashboard, moved 240gb new pool.  now, old pool still complaining low on capacity , should still add 2 more disks expand pool, of disks @ 71%.  interestingly, windows explorer claims 63% of pool used.  (i set size match put on mirrored pool.)

so, question...  why doesn't deleting files pool free space on physical disks , there can free 240gb no longer used?

thanks.

the problem shadow copies.  460 gb worth of shadow copies. 

i used computer management view shadow copy configuration on volume in question right clicking on "shared folders", selecting "all tasks" , "configure shadow copies..." .  using of maximum 10% of drive's size configured for  shadow copies.

using dashboard, right clicked on drive, clicked "view hard drive properties", clicked "shadow copies" tab, , unchecked box.  took 10 minutes, after completed, space free , no longer had alert out of low on capacity.

the following post gave me idea:

http://social.technet.microsoft.com/forums/en-us/winserveressentials/thread/5ca27fd1-81a7-4b14-b00c-77ae2db937e8

Windows Server  >  Windows Server 2012 General