On Thursday 09 July 2015 22:06:09 Hugo Mills wrote: > On Thu, Jul 09, 2015 at 11:34:40PM +0200, Wolfgang Mader wrote: > > Hi, > > > > I have a btrfs raid10 which is connected to a server hosting > > multiple virtual machine. Does btrfs support connecting the same > > subvolumes of the same raid to multiple virtual machines for > > concurrent read and write? The situation would be the same as, say, > > mounting user homes from the same nfs share on different machines. > > It'll depend on the protocol you use to make the subvolumes visible > within the VMs. > > btrfs subvolumes aren't block devices, so that rules out most of > the usual approaches. However, there are two methods I've used which I > can confirm will work well: NFS and 9p. > > NFS will work as a root filesystem, and will work with any > host/guest, as long as there's a network connection between the two. > 9p is, at least in theory, faster (particularly with virtio), but > won't let you boot with the 9p device as your root FS. You'll need > virtualiser support if you want to run a virtio 9p -- I know qemu/kvm > supports this; I don't know if anything else supports it. Thanks for the overview. It it qmeu/kvm in fact, to this is an option. Right now, however, I connect the discs as virtual discs and not the file system, but only to one virtual machine. Best, Wolfgang > > You can probably use Samba/CIFS as well. It'll be slower than the > virtualised 9p, and not be able to host a root filesystem. I haven't > tried this one, because Samba and I get on like a house on fire(*). > > Hugo. > > (*) Screaming, shouting, people running away, emergency services.
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