[Qemu-devel] Sharing files between VMs and hosts

[Mark Williamson]

Hi all,

I can't reply directly to the thread in question because my stupid mailclient 
lost the relevant e-mails, grrrr.

Regarding disk-based file sharing between guest and host, which I saw 
mentioned briefly (although the focus was on network-based sharing):
Some filesystems (e.g. I think Redhat uses one called GFS) which don't make 
the assumption of a single writer.  These would typically be used for multiple 
machines in a cluster accessing a SAN.  It should be possible to use such a 
filesystem on a disk file and simultaneously write it in the guest and in the 
host (which could mount it via loopback, if QEmu disks are just raw disk 
images - are they?).

Using a normal filesystem with multiple writers is guaranteed to result in 
corruption and having a single writer and other readers is likely to confuse 
the readers (they may think the disk is spontaneously corrupting underneath 
them!).

Of course, using special filesystems doesn't fix the windows compatibility 
problem.  Another alternative would be to use NFS and run some kind of NFS 
driver in a Windows VM... (does Cygwin have one?  Microsoft's UNIX 
compatibility kit may have one).

My $0.02,
Cheers,
Mark