title: Suddenly bad disk I/O utilization on SQL-server even on weekend where we have few transactions
body: <p>On friday our MS SQL-server 2012 suddenly showed 100% disk I/O utilization in New Relic (Performance monitor). We hade made no updates what so ever and windows update showed nothing that had happend.
  The load on the server was low because fridays have low traffic on our website. The disk I/O utilization has been kept high even over the weekend.</p>
  
  <p>The server is a VM-Ware machine with 16 procs and 36 gb of memory. The disk are located in a san.</p>
  
  <p>We have about 5 mb of reads per second and very low on writes on the database server.
  The server has about 500 I/O operations per second.
  The CPU is at 25%</p>
  
  <p>The database is stored in 12 files on a separate drive on the server. 
  No long running task are running.
  The server is defragmentet and all the indexeson the database have been rebuilt.</p>
  
  <p>Perfmon on the sql server shows disk que at peek 5.</p>
  
  <p>Our server guys says that the SAN is running smoothly. But my gues is that something happend on that friday whick keeps our SQL have to wait for file operations.</p>
  
  <p>Any ideas?</p>