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<p class="MsoNormal">We are planning a replicated cluster. Due to a combination of purchasing cycles, floor loading and VAT-exemption status for half the equipment/data, this will be built over time using a total 8 Lenovo DSS building blocks. 2 main pools,
in 2 data centres, with 2 DSSG per pool, and a quorum/manager node with a local tie breaker disk in a 3rd physical location.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">My main question is about failure groups - so far, with 2 DSS and 1 tiebreaker, we would have had 1 failure group per DSS and 1 for the tie breaker disk, giving us a total of 3. But if we did that now we would have 9 failure groups in 1
filesystem, which is more than the maximum number of replicas of the file system descriptor and not desirable, as I understand it.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">So we could have either:<o:p></o:p></p>
<ul style="margin-top:0cm" type="disc">
<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo1">1 FG per physical site, and assign all 4 DSS per site to 1 FG, and a 3rd to the tiebreaker<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo1">1 FG per pool per site, with 2 DSS in each FG. This makes sense as the pairs of DSSG will both always need to be up for all the data in the pool to be accessible.
<o:p></o:p></li></ul>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The second option would give us 5 failure groups, but what would be the advantage and disadvantages of more failure groups?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Many thanks,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Luke<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:9.0pt;color:#1F497D;mso-fareast-language:EN-GB">--
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;color:#1F497D;mso-fareast-language:EN-GB">Luke Sudbery<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;color:#1F497D;mso-fareast-language:EN-GB">Principal Engineer (HPC and Storage).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;color:#1F497D;mso-fareast-language:EN-GB">Architecture, Infrastructure and Systems<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;color:#1F497D;mso-fareast-language:EN-GB">Advanced Research Computing, IT Services<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;color:#1F497D;mso-fareast-language:EN-GB">Room 132, Computer Centre G5, Elms Road<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;color:#1F497D;mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:9.0pt;color:#1F497D;mso-fareast-language:EN-GB">Please note I don’t work on Monday.<o:p></o:p></span></b></p>
<p class="MsoNormal"><o:p> </o:p></p>
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