Bug 1031303
Summary: | requesting 'fully allocated' raw volume gives bad performance on btrfs | ||
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Product: | [Community] Virtualization Tools | Reporter: | Gene Czarcinski <gczarcinski> |
Component: | libvirt | Assignee: | Libvirt Maintainers <libvirt-maint> |
Status: | CLOSED NOTABUG | QA Contact: | |
Severity: | medium | Docs Contact: | |
Priority: | unspecified | ||
Version: | unspecified | CC: | acathrow, berrange, crobinso, gscrivan |
Target Milestone: | --- | ||
Target Release: | --- | ||
Hardware: | x86_64 | ||
OS: | Linux | ||
Whiteboard: | |||
Fixed In Version: | Doc Type: | Bug Fix | |
Doc Text: | Story Points: | --- | |
Clone Of: | Environment: | ||
Last Closed: | 2013-11-17 15:56:07 UTC | Type: | Bug |
Regression: | --- | Mount Type: | --- |
Documentation: | --- | CRM: | |
Verified Versions: | Category: | --- | |
oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
Cloudforms Team: | --- | Target Upstream Version: | |
Embargoed: |
Description
Gene Czarcinski
2013-11-16 16:36:16 UTC
OK, I have figure out how to do it but I would like to leave this open. It should be easier to do this directly. The way I did it was to create the VM, then delete the qcow2 disk that got created and create a new virtio disk which came up as a"raw" disk. Did an install of F20-Beta and it was pretty good. First, let me say the chattr +C /var/lib/libvirt/images had been run some time ago. The new file has 15 extents for an 8GB file. Not quite as good as the 7 extents I got using dd if=/dev/zero of=/var/lib/libvirt/images/... but more than good enough. So, the capability is there. The small problem is to be able to specify it up front and I believe the way to do that is to be able to specify the format to be used. BTW, nothing critical here about making it in for F20. If you can point me at where I might look for the code, I might take a shot at coming up with a patch. If you folks feel strongly on how such an option should be specified, please speak up because I do not care. I am just interested in the functionality and am willing to invest some time to make it happen. Also Gene's thread here: https://lists.fedoraproject.org/pipermail/virt/2013-November/003867.html As I am about to mention in that thread, the virt-manager 'new vm' wizard does have an option to 'fully allocate' the new disk image, but it just asks libvirt to do that for us. Libvirt uses fallocate which might not be a good idea on btrfs. So reassigning to libvirt. I did not realize that there was a preference where I could set the storage format to be used by the vm creation wizard for the disk image. Change the value from the "System default (qcow2)" to "raw" and things work as I want them to on my btrfs system. This should be documented someplace but I am not sure where that would be. I will put something up on the libvirt-users mailing list. |