Greetings, I just re-installed my system using the new MSDN ISO's for Windows 10 Enterprise 64-bit from WZorNet. After installing all my default applications, restoring my Steam library and whatnot I decided to NOT install Symantec Endpoint Protection this time around and test out the improved Windows Defender built into Windows 10 just to see how good (or not) it might be. First thing I noticed is the complete lack of advanced options within in Windows 10. It wasn't awesome within Microsoft Security Essentials / Forefront / Security Center Endpoint running on Windows 7, or the one within Windows 8 / 8.1 either but this time around Microsoft have basically stripped out all options. But luckily I figured one can configure quite a lot using GPEdit.msc. Yesterday I started my very first "Full Scan" using Windows Defender in Windows 10. I do normally schedule a Full Scan to be ran at 05.00 ever day on my desktops and servers. Using Symantec Endpoint Protection the scans will normally take from 20 minutes (on the systems running SSD only) and up to 2-4 hours on my file server with it's RAID5 array containing about 17TB of data. Running a Full Scan with Windows Defender in Windows 10 is performing horribly... I started it 23:02 yesterday, so it's been running for 16,5 hours and guess what, it's not done yet. If I' am to judge from the progress bar it still got about 10-15% left until it's done. There are no removable devices attached so there is no slow USB-scanning going on. I have disabled network scanning using GPEdit.msc and I have yet to attach any of my network resources to the machine so it's scanning locale content only. The system got a Samsung 840 Pro 500GB, whereas 200GB has been used. It has a RAID0 array consisting of 3x Intel X-25M Gen2 80GB SSD's where about 100GB out of 240GB has been used and there is a 2TB WD RE4 hard drive with a 250GB Intel 510 SSD as cache whereas about 500-600GB has been used. The system is running 16GB 2133MHz DDR3 RAM, Intel Core i7-3960X @ 4,5GHz on a Rampage IV Extreme motherboard so there is no reason why the hardware should slow anything down. I have even tried to use GPEdit.msc to specifically allow Defender to use more than it's 50% CPU limit which is default. Nothing seems to be working in terms of getting things to scan any more efficient. Looking at Task Manager the related Defender processes are only utilising 0-12% CPU and 150-230MB RAM. There are plenty of spare resources, the computer is sitting completely idle.. Is this considered normal behaviour and scanning speeds using Windows Defender in Windows 10? How on earth is it able to be this inefficient when running full scans? I won't even think about how long it would take to do a full scan of my 17TB array with the built-in Windows Defender within Windows Server 2016.
Full scan usually takes long on/in Windows Defender and it's much depended on the number of files in your system. Basically, it is not about the size of your HDD but the number of files present. However, 16 hours is just to long for a full scan. I would suggest you cancel it, empty your temporary folder, run disk can and do disk cleanup. Restart your system and try the full scan this time around.