<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Sep 9, 2015 at 10:49 AM, Jorick Astrego <span dir="ltr"><<a href="mailto:j.astrego@netbulae.eu" target="_blank">j.astrego@netbulae.eu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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On 09/09/2015 10:14 AM, Richard Neuboeck wrote:
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<font color="#000000">> On 04.09.15 10:02, Simone Tiraboschi wrote:
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<font color="#000000">>> Is there a reason why it has to be exactly replica 3?
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<font color="#000000">>> To have a valid quorum having the system being able to decide witch is
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<font color="#000000">>> the right and safe copy avoiding an issue called split brain.
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<font color="#000000">>> Under certain circumstances/issues (network issue, hosts down or
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<font color="#000000">>> whatever could happen) the data on different replica could diverge: if
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<font color="#000000">>> you have two and just two different hosts that claim each other
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<font color="#000000">> that its
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<font color="#000000">>> copy is the right one there is no way to automatically take the right
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<font color="#000000">>> decision. Having three hosts and setting the quorum according to that
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<font color="#000000">>> solves/mitigates the issue.
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<font color="#000000">> Thanks for the explanation. I do understand the problem but since
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<font color="#000000">> I'm somewhat limited in my hardware options is there a way to
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<font color="#000000">> override this requirement? Meaning if I change the checks for
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<font color="#000000">> replica 3 in the installation scripts does something else fail on
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<font color="#000000">> the way?
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<font color="#000000">> In my case coherence checks would come from outside the storage and
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<font color="#000000">> vm host setup and fencing would be applied appropriately.
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<font color="#000000">> I would very much appreciate it if the particulars of the storage
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<font color="#000000">> setup could be either selected from a list of possibilities or be
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<font color="#000000">> ignored and just a warning be issued that this setup is not recommended.
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<font color="#000000">> Thanks!
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<font color="#000000">> Richard
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As a side question, in Glusterfs 3.7 there is an "AFR arbiter volume"
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(<a href="http://gluster.readthedocs.org/en/release-3.7.0-1/Features/afr-arbiter-volumes/" target="_blank">http://gluster.readthedocs.org/en/release-3.7.0-1/Features/afr-arbiter-volumes/</a>)
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that will only contain the metadata.
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Will ovirt support this in 3.6?<br></div></blockquote><div><br></div><div>Not explicitly and I never tried it with hosted-engine but I suspect it works as far it will report replica level = 3.</div><div><br></div><div>By the way you can save disk space on the third host but you still need three hosts.</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div>
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Kind regards,
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Jorick Astrego
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<b style="color:#604c78"></b><br><br><span style="color:#604c78"><font color="000000"><span lang="NL">Met vriendelijke groet, With kind regards,<br><br>Jorick Astrego<br></span></font></span><b style="color:#604c78"><br>Netbulae Virtualization Experts </b><br><hr style="border:none;border-top:1px solid #ccc"><table style="width:522px"><tbody><tr><td style="width:130px;font-size:10px">Tel: 053 20 30 270</td> <td style="width:130px;font-size:10px"><a href="mailto:info@netbulae.eu" target="_blank">info@netbulae.eu</a></td> <td style="width:130px;font-size:10px">Staalsteden 4-3A</td> <td style="width:130px;font-size:10px">KvK 08198180</td></tr><tr> <td style="width:130px;font-size:10px">Fax: 053 20 30 271</td> <td style="width:130px;font-size:10px"><a href="http://www.netbulae.eu" target="_blank">www.netbulae.eu</a></td> <td style="width:130px;font-size:10px">7547 TA Enschede</td> <td style="width:130px;font-size:10px">BTW NL821234584B01</td></tr></tbody></table><br><hr style="border:none;border-top:1px solid #ccc"><br>
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