Re: [ovirt-users] DISCARD support?
This is a multi-part message in MIME format. --------------DFD541D40E712C15A95C6FB1 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit 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@ecarnot.net <mailto:nicolas@ecarnot.net>> 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 <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-discar... http://www.ovirt.org/develop/release-management/features/storage/wipe-volume... http://www.ovirt.org/develop/release-management/features/storage/discard-aft... Y. Best, -- Nicolas ECARNOT --------------DFD541D40E712C15A95C6FB1 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 8bit <html> <head> <meta http-equiv="content-type" content="text/html; charset=utf-8"> </head> <body bgcolor="#FFFFFF" text="#000000"> <div dir="ltr">Hello,<br> <br> Sending this here to share knowledge.<br> <br> 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.<br> <br> We are using thin-provisioned block storage LUNs (Equallogic), on which oVirt is creating numerous Logical Volumes, and we're very happy with it.<br> When oVirt is removing a virtual disk, the SAN is not informed, because the LVM layer is not sending the "issue_discard" flag.<br> <br> /etc/lvm/lvm.conf is not the natural place to try to change this parameter, as VDSM is not using it.<br> <br> 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.<br> <br> <a class="moz-txt-link-freetext" href="https://bugzilla.redhat.com/show_bug.cgi?id=1342919">https://bugzilla.redhat.com/show_bug.cgi?id=1342919</a><br> <a class="moz-txt-link-freetext" href="https://bugzilla.redhat.com/show_bug.cgi?id=981626">https://bugzilla.redhat.com/show_bug.cgi?id=981626</a><br> <br> -- <br> Nicolas ECARNOT<br> <div class="gmail_extra"><br> <div class="gmail_quote">On Mon, Oct 3, 2016 at 2:24 PM, Nicolas Ecarnot <span dir="ltr"><<a href="mailto:nicolas@ecarnot.net" target="_blank">nicolas@ecarnot.net</a>></span> wrote:<br> <blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Yaniv,<br> <br> As a pure random way of web surfing, I found that you posted on twitter an information about DISCARD support. (<a href="https://twitter.com/YanivKaul/status/773513216664174592" rel="noreferrer" target="_blank">https://twitter.com/YanivKaul<wbr>/status/773513216664174592</a>)<br> <br> 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?<br> <br> 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?<br> </blockquote> <div><br> </div> <div>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.</div> <div>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).</div> <div>We are planning to add this via a UI and API in 4.1.</div> <div>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.</div> <div>See:</div> <div><a href="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/pass-discard-from-guest-to-underlying-storage/</a></div> <div><a href="http://www.ovirt.org/develop/release-management/features/storage/wipe-volumes-using-blkdiscard/">http://www.ovirt.org/develop/release-management/features/storage/wipe-volumes-using-blkdiscard/</a></div> <div><a href="http://www.ovirt.org/develop/release-management/features/storage/discard-after-delete/">http://www.ovirt.org/develop/release-management/features/storage/discard-after-delete/</a></div> <div><br> </div> <div>Y.</div> <div> <br> </div> <blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"> <br> Best,<span class="gmail-HOEnZb"><font color="#888888"><br> <br> -- <br> Nicolas ECARNOT<br> </font></span></blockquote> </div> <br> </div> </div> </body> </html> --------------DFD541D40E712C15A95C6FB1--
On Oct 4, 2016 11:11 AM, "Nicolas Ecarnot" <nicolas@ecarnot.net> wrote:
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
When oVirt is removing a virtual disk, the SAN is not informed, because
oVirt is creating numerous Logical Volumes, and we're very happy with it. 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. Our implementation will be independent of the LVM setting issue_discard, will not be based on it and it won't be needed. Y.
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@ecarnot.net>
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-discar...
http://www.ovirt.org/develop/release-management/features/storage/wipe-volume...
http://www.ovirt.org/develop/release-management/features/storage/discard-aft...
Y.
Best,
-- Nicolas ECARNOT
_______________________________________________ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users
On Tue, Oct 4, 2016 at 11:11 AM, Nicolas Ecarnot <nicolas@ecarnot.net> wrote:
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
This is already included in 4.0, added in: https://gerrit.ovirt.org/58036 However it is disabled by default. To enable discard, you need to enable the irs:discard_enable option. The best way to do this is to create a dropin conf: /etc/vdsm/vdsm.conf.d/50_discard.conf [irs] discard_enable = true And restart vdsm. You need to deploy this file on all hosts. In the next version we want to enable this automatically if the storage domain supports discard, no configuration on the host will be needed. Nir
-- Nicolas ECARNOT
On Mon, Oct 3, 2016 at 2:24 PM, Nicolas Ecarnot <nicolas@ecarnot.net> 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@ovirt.org http://lists.ovirt.org/mailman/listinfo/users
participants (3)
-
Nicolas Ecarnot -
Nir Soffer -
Yaniv Kaul