Re: [ovirt-users] DISCARD support?

Hello, Sending this here to share knowledge. Here is what I learned from many BZ and mailing list posts readings. I'm not working at Redhat, so please correct me if I'm wrong. We are using thin-provisioned block storage LUNs (Equallogic), on which oVirt is creating numerous Logical Volumes, and we're very happy with it. When oVirt is removing a virtual disk, the SAN is not informed, because the LVM layer is not sending the "issue_discard" flag. /etc/lvm/lvm.conf is not the natural place to try to change this parameter, as VDSM is not using it.

Efforts are presently made to include issue_discard setting support directly into vdsm.conf, first on a datacenter scope (4.0.x), then per storage domain (4.1.x) and maybe via a web GUI check-box. Part of the effort is to make sure every bit of a planned to be removed LV get wiped out. Part is to inform the block storage side about the deletion, in case of thin provisioned LUNs. https://bugzilla.redhat.com/show_bug.cgi?id=1342919 https://bugzilla.redhat.com/show_bug.cgi?id=981626

-- Nicolas ECARNOT On Mon, Oct 3, 2016 at 2:24 PM, Nicolas Ecarnot <nicolas(a)ecarnot.net&gt; wrote: > Yaniv, > > As a pure random way of web surfing, I found that you posted on twitter > an information about DISCARD support. (https://twitter.com/YanivKaul > /status/773513216664174592) > > I did not dig any further, but has it any relation with the fact that so > far, oVirt did not reclaim lost storage space amongst its logical volumes > of its storage domains? > > A BZ exist about this, but one was told no work would be done about it > until 4.x.y, so now we're there, I was wondering if you knew more? > Feel free to send such questions on the mailing list (ovirt users or devel), so other will be able to both chime in and see the response. We've supported a custom hook for enabling discard per disk (which is only relevant for virtio-SCSI and IDE) for some versions now (3.5 I believe). We are planning to add this via a UI and API in 4.1. In addition, we are looking into discard (instead of wipe after delete, when discard is also zero'ing content) as well as discard when removing LVs. See: http://www.ovirt.org/develop/release-management/features/ storage/pass-discard-from-guest-to-underlying-storage/ http://www.ovirt.org/develop/release-management/features/ storage/wipe-volumes-using-blkdiscard/ http://www.ovirt.org/develop/release-management/features/ storage/discard-after-delete/ Y. > > Best, > > -- > Nicolas ECARNOT > _______________________________________________ Users mailing list Users(a)ovirt.org http://lists.ovirt.org/mailman/listinfo/users