Oracle Linux: GlusterFS - Use GlusterFS Volumes To Host QEMU-KVM VM Images (Doc ID 2555746.1)

Last updated on MAY 19, 2021

Applies to:

Goal

To guide users how to use GlusterFS Volumes to host QEMU-KVM VM images.

Using GlusterFS volumes to host VM images and data was sub-optimal due to the FUSE overhead involved in accessing gluster volumes via GlusterFS native client. However this has changed now with two specific enhancements:

• A new library called libgfapi is now available as part of GlusterFS that provides POSIX-like C APIs for accessing gluster volumes. libgfapi support is available from GlusterFS-3.4 release.

• QEMU (starting from QEMU-1.3) will have GlusterFS block driver that uses libgfapi and hence there is no FUSE overhead any longer when QEMU works with VM images on gluster volumes.

GlusterFS specifcation in QEMU:

VM image residing on gluster volume can be specified on QEMU command line using URI format

gluster[+transport]://[server[:port]]/volname/image[?socket=...]

• gluster is the protocol.
• transport specifies the transport type used to connect to gluster management daemon (glusterd). Valid transport types are tcp, unix and rdma. If a transport type isn’t specified, then tcp type is assumed.
• server specifies the server where the volume file specification for the given volume resides. This can be either hostname, ipv4 address or ipv6 address. ipv6 address needs to be within square brackets [ ]. If transport type is unix, then server field should not be specified. Instead the socket field needs to be populated with the path to unix domain socket.
• port is the port number on which glusterd is listening. This is optional and if not specified, QEMU will send 0 which will make gluster to use the default port. If the transport type is unix, then port should not be specified.
• volname is the name of the gluster volume which contains the VM image.
• image is the path to the actual VM image that resides on gluster volume.

Examples: