Bug 589975
| Summary: | RFE: virt-manager: allow setting cache mode for kvm/qemu disks | ||
|---|---|---|---|
| Product: | [Fedora] Fedora | Reporter: | Tomasz Torcz <tomek> |
| Component: | virt-manager | Assignee: | Cole Robinson <crobinso> |
| Status: | CLOSED CURRENTRELEASE | QA Contact: | Fedora Extras Quality Assurance <extras-qa> |
| Severity: | medium | Docs Contact: | |
| Priority: | low | ||
| Version: | 13 | CC: | berrange, crobinso, hbrock, jforbes, virt-maint |
| Target Milestone: | --- | ||
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2010-11-26 18:18:52 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
This is upstream now: http://hg.fedorahosted.org/hg/virt-manager/rev/0241648684d1 Indeed, virt-manager in F14 contains cache mode selector. |
Description of problem: On some filesystems (btrfs) default caching in qemu makes guest extremely slow. It could be improved greatly by changing caching to writeback mode. The cost of this change: degraded reliability in case of host crash. Please provide drop-down list to change the mode in Disk details view in virt-manager. Version-Release number of selected component (if applicable): virt-manager-0.8.3-3.fc13.noarch libvirt-0.7.7-3.fc13.x86_64 How reproducible: Always. Steps to Reproduce: 1. Go to disk properties. Actual results: No dropdown list for cache mode. Expected results: Cache mode: dropdown list with options "writethrough (default)", "writeback", "none (Direct_IO)". Nb. I'm not sure if "none" really equals dio. Additional info: It is possible to manually edit guest .xml file to change caching mode. This change is retained by virt-manager and provides requested performance. Example: # grep -C2 cache /etc/libvirt/qemu/scratch-F13-32b.xml <emulator>/usr/bin/qemu-kvm</emulator> <disk type='file' device='disk'> <driver name='qemu' type='raw' cache='writeback'/> <source file='/mnt/storage_ST_250G/vms/scratch-F13-32b.img'/> <target dev='vda' bus='virtio'/> the "cache='writeback'" part was added manually.