Description of problem: On my 2008R2 VM, the write cache settings for a virtio-blk enabled disk is ENABLED. Moreover - it cannot be disabled ("This device does not allow its write-caching setting to be changed" - with an exclamation mark next to it). I can, however, uncheck 'turn off Windows write cache buffer flushing on the device'. Not sure if it's good enough. I'm running the VM via RHEVM 2.2, with a QCOW2 image, cache=none, against a Netapp iSCSI with target with write-through cache settings (as determined via /sys/class/scsi_disk/N:N:N:N/cache_type) Version-Release number of selected component (if applicable): kernel-2.6.18-194.26.1.el5 kvm-83-164.el5_5.26 How reproducible: Always Steps to Reproduce: 1. Via the device manager, locate the virtio-blk based disk, right click on its properties and try to change the caching parameter. 2. 3. Actual results: Expected results: Additional info:
Note: it seems it can be changed in a 2003 guest.
(In reply to comment #0) > Description of problem: > On my 2008R2 VM, the write cache settings for a virtio-blk enabled disk is > ENABLED. Moreover - it cannot be disabled ("This device does not allow its > write-caching setting to be changed" - with an exclamation mark next to it). In our situation it is not possible to change WCE on the working system. WCE can be turned down by specifying cache=writethrough. > I can, however, uncheck 'turn off Windows write cache buffer flushing on the > device'. Not sure if it's good enough. This way one can throttle down or even disable sending of flush requests from a file system driver. I'm going to close this bug as NOTABUG. Please feel free to reopen this bug in 6.3 if you think different.