sql server - How to find rolling daily average -

sql server - How to find rolling daily average -

i'm trying figure out daily disk usage on servers, have powershell script writing next table every morning:

create table [dbo].[diskinfo_sj]( [systemname] [sysname] null, [deviceid] [sysname] null, [volumename] [sysname] null, [size] [decimal](18, 2) null, [freespace] [decimal](18, 2) null, [adddate] [datetime] null ) on [primary]

sample info like:

systemname deviceid volumename size freespace adddate acsql751 c: 146799554560.00 84255379456.00 2014-10-13 13:16:52.910 acsql751 d: localdisk 81586515968.00 75507929088.00 2014-10-13 13:16:52.910 acsql751 f: sanvol2 156757352448.00 146196172800.00 2014-10-13 13:16:52.910 aegissql02 c: 73364254720.00 16627585024.00 2014-10-13 13:16:52.910

what come script takes weekly average , projects when drive run out of info if average accurate.

sql-server tsql powershell