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    <title>MongoDB Jira</title>
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    <description>This file is an XML representation of an issue</description>
    <language>en-us</language>    <build-info>
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        <build-number>970001</build-number>
        <build-date>13-04-2023</build-date>
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<item>
            <title>[DOCS-4037] Mongod and VMware vmmemctl (balloon driver) needs an official explanation</title>
                <link>https://jira.mongodb.org/browse/DOCS-4037</link>
                <project id="10380" key="DOCS">Documentation</project>
                    <description>&lt;p&gt;The balloon driver for VMWare (or Xen, Hyper-V,etc) seems like is not compatible with &lt;b&gt;mongod&lt;/b&gt;.&lt;/p&gt;

&lt;p&gt;The explanation about the balloon driver utility is the following:&lt;/p&gt;

&lt;div class=&quot;panel&quot; style=&quot;border-width: 1px;&quot;&gt;&lt;div class=&quot;panelContent&quot;&gt;
&lt;p&gt;If a database VM needs to compete for the same physical memory space with other VMs, the hypervisor could start allocating memory on disk.&lt;/p&gt;

&lt;p&gt;Using vmmemctl (balloon driver), if the hypervisor decides that it wants to reduce the amount of physical memory used by the VM, the driver starts to perform memory allocations inside the VM pushing out other memory data to disk (to the swap space).&lt;/p&gt;

&lt;p&gt;This behaviour is highly desirable in general, because otherwise the hypervisor would have to allocate the VM memory data in it&apos;s own swap file. In that case the OS believes that it has allocated physical memory, and the application will experience some unexplainable delays and result in performance problems.&lt;/p&gt;
&lt;/div&gt;&lt;/div&gt;

&lt;p&gt;The main concern with the balloon driver relates to the experience of some of our customers in which crashes no longer occur when the driver is disabled.&lt;/p&gt;

&lt;p&gt;I found a &lt;a href=&quot;http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&amp;amp;docType=kc&amp;amp;externalId=1003586&amp;amp;sliceId=1&amp;amp;docTypeID=DT_KB_1_1&amp;amp;dialogID=390330968&amp;amp;stateId=1%200%20368230845&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;bug in the driver&lt;/a&gt; related to &lt;b&gt;mmap&lt;/b&gt; allocation. IMHO VMware bug KB1003586 do not affect &lt;b&gt;mongod&lt;/b&gt; because it don&apos;t pin or lock memory pages (&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-8121&quot; title=&quot;mlock text segment&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-8121&quot;&gt;&lt;del&gt;SERVER-8121&lt;/del&gt;&lt;/a&gt;) for now.&lt;/p&gt;

&lt;p&gt;Our recommendation is to disable the balloon driver, but I might add the need for reserve sufficient physical memory in the hypervisor for the VM to ensure the database&#8217;s working set fits within it.&lt;/p&gt;</description>
                <environment></environment>
        <key id="157927">DOCS-4037</key>
            <summary>Mongod and VMware vmmemctl (balloon driver) needs an official explanation</summary>
                <type id="3" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14718&amp;avatarType=issuetype">Task</type>
                                            <priority id="3" iconUrl="https://jira.mongodb.org/images/icons/priorities/major.svg">Major - P3</priority>
                        <status id="6" iconUrl="https://jira.mongodb.org/images/icons/statuses/closed.png" description="The issue is considered finished, the resolution is correct. Issues which are closed can be reopened.">Closed</status>
                    <statusCategory id="3" key="done" colorName="success"/>
                                    <resolution id="9">Done</resolution>
                                        <assignee username="michael.paik">Michael Paik</assignee>
                                    <reporter username="ricardo.lorenzo">Ricardo Lorenzo</reporter>
                        <labels>
                            <label>hypervisor</label>
                            <label>vmware</label>
                    </labels>
                <created>Fri, 12 Sep 2014 15:33:15 +0000</created>
                <updated>Mon, 30 Oct 2023 21:51:11 +0000</updated>
                            <resolved>Fri, 3 Apr 2015 22:58:45 +0000</resolved>
                                                    <fixVersion>Server_Docs_20231030</fixVersion>
                                    <component>manual</component>
                        <due></due>
                            <votes>0</votes>
                                    <watches>3</watches>
                                                                                                                <comments>
                            <comment id="1338511" author="emily.hall" created="Wed, 27 Jul 2016 19:10:40 +0000"  >&lt;p&gt;Closed for housekeeping on 7/27/2016 by Emily Hall. &lt;br/&gt;
If you require additional support, please open a new ticket for prioritization. &lt;br/&gt;
Thanks,&lt;br/&gt;
Emily&lt;/p&gt;</comment>
                            <comment id="872721" author="xgen-internal-githook" created="Fri, 3 Apr 2015 22:58:30 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;username&apos;: u&apos;mpaik&apos;, u&apos;name&apos;: u&apos;Michael Paik&apos;, u&apos;email&apos;: u&apos;michael.paik@10gen.com&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/DOCS-4037&quot; title=&quot;Mongod and VMware vmmemctl (balloon driver) needs an official explanation&quot; class=&quot;issue-link&quot; data-issue-key=&quot;DOCS-4037&quot;&gt;&lt;del&gt;DOCS-4037&lt;/del&gt;&lt;/a&gt;&lt;br/&gt;
Branch: master&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/docs/commit/f137430b479fc6f765575c595f32f7ff8aaf141c&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/docs/commit/f137430b479fc6f765575c595f32f7ff8aaf141c&lt;/a&gt;&lt;/p&gt;</comment>
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