| Summary: | discard is missing from the / mount options | ||
|---|---|---|---|
| Product: | [oVirt] ovirt-node | Reporter: | Fabian Deutsch <fdeutsch> |
| Component: | Installation & Update | Assignee: | Yuval Turgeman <yturgema> |
| Status: | CLOSED CURRENTRELEASE | QA Contact: | Qin Yuan <qiyuan> |
| Severity: | medium | Docs Contact: | |
| Priority: | high | ||
| Version: | 4.0 | CC: | bugs, cshao, ycui |
| Target Milestone: | ovirt-4.0.7 | Flags: | rule-engine:
ovirt-4.0.z?
fdeutsch: ovirt-4.1? fdeutsch: planning_ack? fdeutsch: devel_ack+ ycui: testing_ack+ |
| Target Release: | --- | ||
| Hardware: | Unspecified | ||
| OS: | Unspecified | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | If docs needed, set a value | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2016-12-20 11:38:47 UTC | Type: | Bug |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | Node | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
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Description
Fabian Deutsch
2016-11-25 16:44:55 UTC
There is a systemd timer that runs fstrim periodically. Configure it to run once a day - more efficient than the above. I actually wonder if the fstrim service is a higher risk. Because the service is calling fstrim -a which will trim all mounted file-systems which support discard - and the mounted filesystms are pretty unpredictable. By relying on the discard mount option we ensure that only "our" file-systems will be trimmed. Another thing to conside ris that a fstrim timer is probably as unpredictable as a garbage collector: It will kick in at some point an might degrade performance - and the runtime depends on the pilled up data to be freed. We've got a spike behavior. By using the mount option we have a constant - but more predeictive impact, as we don't pile up a mount of data to be freed. (In reply to Fabian Deutsch from comment #2) > I actually wonder if the fstrim service is a higher risk. > Because the service is calling fstrim -a which will trim all mounted > file-systems which support discard - and the mounted filesystms are pretty > unpredictable. It is predictable and safe. People have been doing it (unknowingly) for several Fedora releases. > > By relying on the discard mount option we ensure that only "our" > file-systems will be trimmed. > > Another thing to conside ris that a fstrim timer is probably as > unpredictable as a garbage collector: It will kick in at some point an might > degrade performance - and the runtime depends on the pilled up data to be > freed. We've got a spike behavior. It has no performance impact these days. It used to, in the distant past. > > By using the mount option we have a constant - but more predeictive impact, > as we don't pile up a mount of data to be freed. Anyway, moving to 4.0.7. Not critical. If it is as in comment 3 then it should really not make a difference - and the service solution is easier. Fabian, discard was already set to / from the mount options since RHVH 4.0 GA.. The block device reclaim space freed. Let's see the final solution by devel. |