Il 17/03/2013 21:58, d hee ha scritto: > What is the current state of SSD Trim/Discard support for a Qemu/KVM > guests? > > I run a Qemi/ KVM host wtih these kvm guests...they are all Linux os's > and use raw images: 1) 20 gig Linux web-server 2) Subsonic music > streaming server for my Android phone 3) Postfix server for automated > emails 4) Linux guest for sandbox for testing. All of this is on my on > personal system as a hobby and not a a business "production" system. If > I run them off a ssd drive without the trim support, will I see > performance impacted as the guest blocks slowly fill up without being > marked for reuse?
DISCARD is finally supported in qemu.git. It is experimental in all released versions. To get trim support you need to do all of the following: 2) use virtio-scsi or another SCSI HBA (IDE would work too, but it is slow); 2) compile qemu.git from master and add ",discard=on" to the "-drive" option; or for released versions add ",discard_granularity=4096" to the "-device" options for disks. For more informations on "-drive" and "-device" check out the docs/qdev-device-use.txt file. 3) mount the filesystems with the discard option in the guest, or periodically run fstrim in the guest; 4) either run the images directly from a partition or logical volume, or mount the filesystems with the discard option in the host, or periodically run fstrim in the host. Paolo
