[vdsm] [RFC] GlusterFS domain specific changes

Federico Simoncelli fsimonce at redhat.com
Fri Aug 3 12:34:24 UTC 2012


----- Original Message -----
> From: "M. Mohan Kumar" <mohan at in.ibm.com>
> To: vdsm-devel at lists.fedorahosted.org
> Sent: Wednesday, July 25, 2012 1:26:15 PM
> Subject: [vdsm] [RFC] GlusterFS domain specific changes
> 
> 
> We are developing a GlusterFS server translator to export block devices
> as regular files to the client. Using block devices to serve VM images
> gives performance improvements, since it avoids some file system
> bottlenecks in the host kernel. Goal is to use one block device(ie file
> at the client side) per VM image and feed this file to QEMU to get the
> performance improvements. QEMU will talk to glusterfs server directly
> using libgfapi.
> 
> Currently we support only exporting Volume groups and Logical
> Volumes. Logical volumes are exported as regular files to the client.
> 
> In GlusterFS terminology a volume capable of exporting block devices is
> created by specifying the 'Volume Group' (ie VG in Logical Volume
> management). Block Device translator(BD xlator) exports this volume
> group as a directory and LVs under it as regular files. In the gluster
> mount point creating a file results in creating a logical volume,
> removing a file results in removing logical volume etc.
> 
> When a GlusterFS volume enabled with BD xlator is used, directory
> creation in that gluster mount path is not supported because directory
> maps to Volume groups in BD xlator. But it could be an issue in VDSM
> environment when a new VDSM volume is created for GlusterFS domain, VDSM
> mounts the storage domain and creates directories under that and create
> files for vm image and other uses (like meta data).
> 
> Is it possible to modify this behavior in VDSM to use flat structure
> instead of creating directories and VM images and other files underneath
> it? ie for GlusterFS domain with BD xlator VDSM will not create any
> directory and only creates all required files under the mount point
> directory itself.



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