SQL server peak hour

You need to monitor and then report against those monitors.

"It depends". What exactly do you mean by "peak"? Peak number of queries? Peak number of reads/writes? of bytes read/written? of CPU usage?

For example, you could take regular snapshots of the results of sp_monitor, and use that to identify the busiest periods. Or, if you're more interested in particular databases, log and report against the output from

select * from ::fn_virtualfilestats(-1,-1)

Or you could look at the appropriate DMVs, for example those particularly related to the SQL Server OS, or the I/O subsystems.

EDIT

OK, so you've indicated you're interested in the file stats. What I do (because I'm monitoring multiple servers on multiple versions of SQL), is capture at a central database the output from the following query, run every 10 minutes:

SELECT convert(varchar(128), Serverproperty('servername')) AS Server,
   convert(varchar(128), Db_name(dbid)) AS DatabaseName,
   fileid,
   timestamp,
   numberreads,
   numberwrites,
   bytesread,
   byteswritten,
   iostallms
FROM   ::fn_virtualfilestats(-1, -1)

I then use the following query against that table to form the basis of any reports:

WITH vfs
 AS (SELECT Row_number() OVER (ORDER BY server, databasename, fileid, datechecked) AS ID,
            Server, DatabaseName, FileID, Timestamp, NumberReads, NumberWrites, BytesRead, BytesWritten, IOStallMS, DateChecked
     FROM   dbo.virtualfilestats),
 vfs1 AS (SELECT * from vfs),
 vfs2 AS (SELECT * FROM vfs)
SELECT vfs1.Server,
   vfs1.DatabaseName,
   vfs1.FileID,
   vfs1.DateChecked                      AS StartDate,
   vfs2.DateChecked                      AS EndDate,
   CASE WHEN vfs2.NumberReads > vfs1.NumberReads THEN
   vfs2.NumberReads - vfs1.NumberReads   ELSE 0 END AS Reads,
   CASE WHEN vfs2.NumberWrites > vfs1.NumberWrites THEN
   vfs2.NumberWrites - vfs1.NumberWrites ELSE 0 END AS Writes,
   CASE WHEN vfs2.BytesRead > vfs1.BytesRead Then
   vfs2.BytesRead - vfs1.BytesRead       ELSE 0 END AS BytesRead,
   CASE WHEN vfs2.BytesWritten > vfs1.BytesWritten THEN
   vfs2.BytesWritten - vfs1.BytesWritten ELSE 0 END AS BytesWritten,
   CASE WHEN vfs2.IOStallMS > vfs1.IOStallMS THEN
   vfs2.IOStallMS - vfs1.IOStallMS       ELSE 0 END AS IOStallMS
FROM   vfs1
   JOIN vfs2
     ON vfs1.server = vfs2.server
        AND vfs1.databasename = vfs2.databasename
        AND vfs1.fileid = vfs2.fileid
        AND vfs1.id = vfs2.id - 1
        AND vfs2.DateChecked IS NOT NULL