[ovirt-users] How do I get discard working?

[Chris Jones - BookIt.com Systems Administrator]

Looks like I need to learn how to use VDSM hooks. I'll start there. 
Thanks everyone.

On 06/10/2015 04:18 PM, Amador Pahim wrote:
> On 06/10/2015 03:24 PM, Fabian Deutsch wrote:
>> ----- Original Message -----
>>> oVirt Node - 3.5 - 0.999.201504280931.el7.centos
>>>
>>> Using our shared storage via baremetal (stock CentOS 7) -> iscsi, I can
>>> successfully issue fstrim commands. With oVirt at the VM level, even
>>> with direct LUNS, trim commands are not supported despite having the LVM
>>> config in the VMs set up to allow it.
>> Hey,
>>
>> IIUIC you try to get discard working for VMs? That means that if
>> fstrim is
>> used inside the VM, that it is getting passed down?
>>
>> The command line needed for qemu to support discards is:
>>
>> $ qemu … -drive if=virtio,cache=unsafe,discard,file=<disk> …
>>
>> I'm not sure which qemu disk drivers/busses support this, but at least
>> virtio does so.
>> I'm using it for development.
>>
>> You could try a vdsm hook to modify the qemu command which is called
>> when the VM is spawned.
>>
>> Let me know if you can come up with a hook to realize this!
>
> There's this hook in code review intended  to do so:
> https://gerrit.ovirt.org/#/c/29770/
>
>>
>> Greetings
>> fabian
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>
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