Marc_G2 Posted November 9, 2019 Share Posted November 9, 2019 (edited) I noticed I was getting poor SSD (Crucial MX300) write performance (about 100 MB/s or less) in my Windows 10 VM. The SSD was mounted using Unassigned Devices. I noticed Windows referred to the VirtIO drive as a SCSI device. So I tried changing "Primary vDisk Bus" to SATA to see if it would help. That didn't help, and it ended up causing other issues including stuttering/cracking audio. The MSI fix doesn't seem to work. Switching back to VirtIO doesn't allow Windows to boot. What performance should I expect from my SSD? Was my problem a VirtIO configuration issue? EDIT. Will try a fresh install and passing though the SSD. Edited November 9, 2019 by Marc_G2 Quote Link to comment
Squid Posted November 9, 2019 Share Posted November 9, 2019 A problem with the default vdisk method is that the vdisk itself cannot be trimmed which means that performance will gradually suffer. Try this: https://forums.unraid.net/topic/51703-vm-faq/#comment-557606 1 Quote Link to comment
Marc_G2 Posted November 9, 2019 Author Share Posted November 9, 2019 I will give this a try before trying to pass though the SSD. Although I was only using 50/500 GB I had available. Quote Link to comment
Marc_G2 Posted November 9, 2019 Author Share Posted November 9, 2019 (edited) Well I managed to get VM booting with VirtIO again. I needed to initialize my newly created disk in Windows Disk Management prior to switching the primary disk to use VirtIO. A quick file copy test shows sustained writes are still less than 100 MB/s. For some reason, Windows won't let me defragment the SSD. It says "Optimization not available" on its status. I'm pretty sure the XML is correct: <disk type='file' device='disk'> <driver name='qemu' type='raw' cache='writeback' discard='unmap'/> <source file='/mnt/disks/Crucial_CT525MX300SSD1_163213963944/Windows 10/vdisk1.img'/> <backingStore/> <target dev='hdc' bus='virtio'/> <boot order='1'/> <alias name='virtio-disk2'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/> Edited November 9, 2019 by Marc_G2 Quote Link to comment
Squid Posted November 9, 2019 Share Posted November 9, 2019 Did you follow the directions in the link? Does it show in Defrag as a Thin Provisioned Drive? Quote Link to comment
Marc_G2 Posted November 9, 2019 Author Share Posted November 9, 2019 I believe the config is correct (see above). The media type says it's a "Solid state drive" and doesn't say it's a thin provisioned drive. So I'm not sure where I went wrong. Quote Link to comment
Marc_G2 Posted November 9, 2019 Author Share Posted November 9, 2019 I created a new VM while passing though the SSD. Sustained write speed is now 200+ MB/s. Definitely better, but still not close to bare metal. Crystal diskmark gave bad results due to caching. For perspective, this is what Space Invader One got for a Vdisk. He had similarly bad sequential write speeds. https://youtu.be/QaB9HhpbDAI?t=15m44s Should I still configure the disk to as a "thin provisioned drive"? Quote Link to comment
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