Bug 689252
| Summary: | Write caching for virtio-blk disk is ENABLED and cannot be disabled (within a 2008R2 guest) | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 5 | Reporter: | Yaniv Kaul <ykaul> |
| Component: | kvm | Assignee: | Vadim Rozenfeld <vrozenfe> |
| Status: | CLOSED NOTABUG | QA Contact: | Virtualization Bugs <virt-bugs> |
| Severity: | medium | Docs Contact: | |
| Priority: | unspecified | ||
| Version: | 5.6 | CC: | gcosta, jkt, mkenneth, rhod, virt-maint |
| Target Milestone: | rc | ||
| Target Release: | --- | ||
| Hardware: | x86_64 | ||
| OS: | Windows | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2011-08-11 16:13:48 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Bug Depends On: | |||
| Bug Blocks: | 580948 | ||
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. |
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: