Hi, I''m running into problems with using DRBD as a backend for a DomU. It says: [ 3.801589] blkfront: barrier: write xvda2 op failed [ 3.801597] blkfront: xvda2: barrier or flush: disabled [ 3.801611] end_request: I/O error, dev xvda2, sector 52171168 [ 3.801630] end_request: I/O error, dev xvda2, sector 52171168 [ 3.801642] Buffer I/O error on device xvda2, logical block 6521396 [ 3.801652] lost page write due to I/O error on xvda2 [ 3.801755] Aborting journal on device xvda2. [ 3.804415] EXT3-fs (xvda2): error: ext3_journal_start_sb: Detected aborted journal [ 3.804434] EXT3-fs (xvda2): error: remounting filesystem read-only [ 3.814754] journal commit I/O error For more detail about my error, see [1] In short: Dom0 is Debian 6, Xen 4.0.1, kernel 2.6.32-5-xen-amd64, DRBD 8.3.7. DomU is Ubuntu 12.04, kernel 3.2.0-24-generic (pvops). It doesn''t matter if I set no-disk-barrier in DRBD. Looking at [2] and [3], it seems that it has to do with false advertising of barriers. But, when I configure DRBD not to use barriers (and xenstore-ls says feature-barrier=0), the DomU still fails with the above error. There is also a Ubuntu lauchpad bugreport which was classified as invalid. I have two main questions: 1): If I understand correctly, when not using barriers, I also don''t use flush-cache because that feature isn''t advertised (xenstore-ls doesn''t mention it, and there was a bug somewhere, right?). So, does that mean when I disable barrier in fstab, I run the risk of data loss (upon power failure, for instance)? 2): Exactly where is this bug? I''m getting completely confused about xen-blkback, xen-blkfront, lvm, etc. And where does it need to be fixed? The xen-blkback on the Dom0? Xen-blkfront on the DomU? So my Debian host, my Ubuntu guest...? [1] http://serverfault.com/questions/393982/xen-domu-on-drbd-device-barrier-errors [2] http://old-list-archives.xen.org/archives/html/xen-devel/2011-09/msg00180.html [3] http://www.gossamer-threads.com/lists/xen/users/226266 [4] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/824089?comments=all