Windows 7, Solid State Drives and Why A WinSAT Score Matters
I was doing a WDRAP and I ran across an interesting case that required me to do some digging that I thought I’d share this out in one source. When we took an xbootmgr trace which we do with all our WDRAPs we saw broken readyboot that was identical to what I talked about here. http://blogs.technet.com/b/markmoro/archive/2011/11/28/xbootmgr-part-2-readyboot-basics.aspx. No cache hits and a lot of cache misses. I explained what readyboot does and how it’s suppose to work and the hotfix that we can roll out to help remediate this in their environment. Then they asked me a great question, “Does this still matter if it is a solid state drive (SSD)?” The answer is no when an SSD is detected the following things are not used, readyboot, readyboost, Superfetch and disk defragmentation. http://blogs.msdn.com/b/e7/archive/2009/05/05/support-and-q-a-for-solid-state-drives-and.aspx . The disk defragmentation service will be set to still run but no disks will be selected.
So now the next question is why is Windows not detecting that the hard drive is a SSD. The first thing we attempted was to update the firmware of the SSD as it was out of date. We rebooted and checked the Superfetch service which was still running meaning that the OS still hasn’t picked up the disk as a SSD. Ok clearly this was something else. After doing some research I learned the following. The Superfetch service looks at the following registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winsat\DiskScore every 30 minutes. If the regkey is 65 or greater, which means the disk has the performance of an SSD, it sets the Superfetch service to manual. This score is populated by the actual WinSAT Primary Hard Disk score. Our next step was to check the WinSAT score for this machine. This is what we found.
Ok so that explains it, the WinSAT has never run on this computer. When is this suppose to run? It runs initially on start up to determine Aero performance and the rest is suppose to fully populate when the machine is idle via a scheduled task. The schedule tasks is under Microsoft\Windows\Maintenance\WinSAT. We found that during the image process this tasks was being disabled so it never ran and thus, never detected the machine had an SSD. Once we kicked of that scheduled task, it rated the Hard Disk at 7.1 the reg key had a value of 71, we waited about 20 minutes and all services were stopped and set appropriately. Case closed.
Mark “my hard disk score goes to 11” Morowczynski