The following was observed in connection with running Xen.

Both replicate backends have 0x00000001 xattr, strongly indicating that
the decrementing xattrop was never called. The client log shows that after many
writes, release was called, with flush never being called. And replicate does
the decrement only in flush.

[2009-08-20 14:26:02] T [fuse-bridge.c:1567:fuse_write] glusterfs-fuse: 8991: WRITE (0x70c9f
b0, size=2560, offset=107126784)
[2009-08-20 14:26:02] T [fuse-bridge.c:1528:fuse_writev_cbk] glusterfs-fuse: 8991: WRITE =>
2560/2560,107126784/8589934594
[2009-08-20 14:26:06] T [fuse-bridge.c:1610:fuse_release] glusterfs-fuse: 8992: RELEASE 0x70
c9fb0

This is further corroborated by the server logs:

[2009-08-20 14:26:02] T [server-protocol.c:3973:server_writev] brick: 36538: WRITEV 'fd=0 (1
776309); offset=111030272; size=2560
[2009-08-20 14:26:02] T [server-protocol.c:3973:server_writev] brick: 36539: WRITEV 'fd=0 (1
776309); offset=107125248; size=1536
[2009-08-20 14:26:02] T [server-protocol.c:3973:server_writev] brick: 36540: WRITEV 'fd=0 (1
776309); offset=107126784; size=2560
[2009-08-20 14:26:06] T [server-protocol.c:4027:server_release] brick: 36541: RELEASE 'fd=0'

Kernel version: 2.6.18-128.1.10.el5xen
fuse init (API version 7.8)
fuse distribution version: 2.7.4