<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><br><br><div id="AppleMailSignature">Bernd Lentes</div><div><br>Anfang der weitergeleiteten Nachricht:<br><br></div><blockquote type="cite"><div><b>Von:</b> "Lentes, Bernd" <<a href="mailto:bernd.lentes@helmholtz-muenchen.de">bernd.lentes@helmholtz-muenchen.de</a>><br><b>Datum:</b> 29. August 2018 um 23:32:49 MESZ<br><b>An:</b> Lars Ellenberg <<a href="mailto:lars.ellenberg@linbit.com">lars.ellenberg@linbit.com</a>><br><b>Betreff:</b> <b>Aw: [DRBD-user] confused with DRBD 9.0 and dual-primary, multi-primary, multi-secondary ...</b><br><br></div></blockquote><blockquote type="cite"><div><span></span><br><span></span><br><span></span><br><blockquote type="cite"><span>Am 29.08.2018 um 16:47 schrieb Lars Ellenberg <<a href="mailto:lars.ellenberg@linbit.com">lars.ellenberg@linbit.com</a>>:</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><blockquote type="cite"><span>On Wed, Aug 29, 2018 at 03:38:34PM +0200, Lentes, Bernd wrote:</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>Hi,</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>i found: </span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>"With current DRBD-9.0 version running in Dual-Primary mode is not recommended (because of lack of testing).</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>In DRBD-9.1 it will be possible to have more than two primaries at the same time."</span><br></blockquote></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>The answer to your actual question is "Yes", below.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>But read on, I try to give a more general answer for</span><br></blockquote><blockquote type="cite"><span>"Can DRBD 9 do multi-primary?" first.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>Even with DRBD 9, we can NOT do "multi-primary", but only "two-primary".</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>If you start playing around, it may at first *seem* like it would work.</span><br></blockquote><blockquote type="cite"><span>It does not.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>And *if* you do go "two-primary", that also means two nodes only.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>NOT two-primary plus multiple secondaries.</span><br></blockquote><blockquote type="cite"><span>Does not work either, unfortunately.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>With the notable exception of live-migration in a multi-peer setup,</span><br></blockquote><blockquote type="cite"><span>where we have "two" primaries with potentially "many" secondary peers.</span><br></blockquote><blockquote type="cite"><span>But only for a short time, and these are not actually concurrently</span><br></blockquote><blockquote type="cite"><span>written to, so that's a special case.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>What I think we want to support at some point even in the "9.0" series</span><br></blockquote><blockquote type="cite"><span>is two-primaries plus one or more secondaries. Maybe.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>"N >= 3" Primaries is something that will come only</span><br></blockquote><blockquote type="cite"><span>in some later "9.1" (or 9.2 or 10.x or 23.y) version.</span><br></blockquote><blockquote type="cite"><span>If at all. We don't see a "real" use case for this.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><blockquote type="cite"><span>Clear statement. I'm using SLES 12 SP3 with DRBD 9.0.8.</span><br></blockquote></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>If you want DRBD 9, you should be prepared to keep track of,</span><br></blockquote><blockquote type="cite"><span>and regularly upgrade to, upcoming DRBD 9 releases.</span><br></blockquote><blockquote type="cite"><span>Currently we are at 9.0.15.</span><br></blockquote><blockquote type="cite"><span>You should certainly not stay on 9.0.8.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>If you really want/need "real, concurrent" dual-primary DRBD,</span><br></blockquote><blockquote type="cite"><span>(which is most likely a bad idea anyways;</span><br></blockquote><blockquote type="cite"><span>there are very limited use cases where dual-primary is actually useful</span><br></blockquote><blockquote type="cite"><span>beyond being "cool" or apparently, but not actually, "convenient")</span><br></blockquote><blockquote type="cite"><span>For now I'd suggest to stay with 8.4,</span><br></blockquote><blockquote type="cite"><span>because that emphasizes the "two node only" aspect.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>If you only need the "short time, not really concurrent" dual-primary</span><br></blockquote><blockquote type="cite"><span>for "live migration" in a virtualization environment,</span><br></blockquote><blockquote type="cite"><span>both DRBD 8.4 and DRBD 9 can do that,</span><br></blockquote><blockquote type="cite"><span>and this is one of the main use cases for LINSTOR with DRBD 9.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><blockquote type="cite"><span>The kernel modules are 9.0.x.</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>The drbd-utils i found are 9.x.</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>Are these already dual-primary capable ?</span><br></blockquote></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>Yes.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>But *really* at least upgrade to 9.0.15,</span><br></blockquote><blockquote type="cite"><span>and then .16 and .17 and ... when they come out.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>If that's not something you can do in your environment,</span><br></blockquote><blockquote type="cite"><span>stay with the stable-and-frozen DRBD 8.4 series.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>Or look into our LINSTOR project, which requires DRBD 9, and is supposed</span><br></blockquote><blockquote type="cite"><span>to make integration with various virtualization solutions much easier.</span><br></blockquote><blockquote type="cite"><span>Still, also in that case,</span><br></blockquote><blockquote type="cite"><span>prepare to regularly upgrade both DRBD 9 and LINSTOR components.</span><br></blockquote><blockquote type="cite"><span>There will be bugs, and bug fixes, and they will be relevant for your</span><br></blockquote><blockquote type="cite"><span>environment.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>-- </span><br></blockquote><blockquote type="cite"><span>: Lars Ellenberg</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><span></span><br><span>Hi Lars,</span><br><span></span><br><span>thanks for this very profound answer.</span><br><span></span><br><span>Bernd</span></div></blockquote>
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