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    <title>MongoDB Jira</title>
    <link>https://jira.mongodb.org</link>
    <description>This file is an XML representation of an issue</description>
    <language>en-us</language>    <build-info>
        <version>9.7.1</version>
        <build-number>970001</build-number>
        <build-date>13-04-2023</build-date>
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<item>
            <title>[SERVER-5670] externally preallocated data files may be ignored when allocating extents </title>
                <link>https://jira.mongodb.org/browse/SERVER-5670</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;In the following scenario externally preallocated data files may be skipped:&lt;/p&gt;

&lt;p&gt;1) data files (test.0,1,2,...) are allocated manually (for example with dd).&lt;br/&gt;
2) Mongod is started and database &apos;test&apos; is created to use these data files.&lt;br/&gt;
3) Mongod is restarted, and the &apos;test&apos; database is opened.  Because the database already exists at the time it is opened, openAllFiles() is called which increments the database&apos;s &apos;n&apos; to the total number of existing data files minus one.&lt;br/&gt;
4) A collection in the test database grows in size, with growing extent sizes, until the followupSize() call to determine a new collection size returns Extent::maxSize().&lt;br/&gt;
5) Database::suitableFile() is called with Extent::maxSize().  No data file under the Database&apos;s &apos;n&apos; limit can fit an extent of this size because the specified max extent size is equal to the max file size and some room is needed for the file header.&lt;br/&gt;
6) Database::suitableFile() fails to identify an existing file (under the &apos;n&apos; limit) that can fit an extent of Extent::maxSize(), so it allocates a new file with addAFile() and returns that new file.&lt;br/&gt;
7) Subsequent extent allocations also request a file for an extent of size Extent::maxSize() and skip the unused files as well.&lt;/p&gt;

&lt;p&gt;I did this to demonstrate the issue:&lt;/p&gt;

&lt;p&gt;I manually preallocated some data files&lt;/p&gt;
&lt;p/&gt;
&lt;div id=&quot;syntaxplugin&quot; class=&quot;syntaxplugin&quot; style=&quot;border: 1px dashed #bbb; border-radius: 5px !important; overflow: auto; max-height: 30em;&quot;&gt;
&lt;table cellspacing=&quot;0&quot; cellpadding=&quot;0&quot; border=&quot;0&quot; width=&quot;100%&quot; style=&quot;font-size: 1em; line-height: 1.4em !important; font-weight: normal; font-style: normal; color: black;&quot;&gt;
		&lt;tbody &gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;  margin-top: 10px;   margin-bottom: 10px;  width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;for i in `seq 0 29`; do dd if=/dev/zero of=test.$i bs=8192 count=262016 ; done&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
			&lt;/tbody&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;p/&gt;

&lt;p&gt;I started mongod and began running this script&lt;/p&gt;
&lt;p/&gt;
&lt;div id=&quot;syntaxplugin&quot; class=&quot;syntaxplugin&quot; style=&quot;border: 1px dashed #bbb; border-radius: 5px !important; overflow: auto; max-height: 30em;&quot;&gt;
&lt;table cellspacing=&quot;0&quot; cellpadding=&quot;0&quot; border=&quot;0&quot; width=&quot;100%&quot; style=&quot;font-size: 1em; line-height: 1.4em !important; font-weight: normal; font-style: normal; color: black;&quot;&gt;
		&lt;tbody &gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;  margin-top: 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;db.createCollection( &apos;c&apos;, { autoIndexId:false } );&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;big = new Array( 1000000 ).toString();&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;while( 1 ) {&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    db.c.insert( { b:big } );&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    db.getLastError();&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   margin-bottom: 10px;  width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;}&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
			&lt;/tbody&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;p/&gt;

&lt;p&gt;I let the script run for a little while, then stopped and restarted mongod and ran the script again.  Most of the data files that were unused by the prior mongod session remained unused as new data files were allocated.&lt;/p&gt;</description>
                <environment></environment>
        <key id="36827">SERVER-5670</key>
            <summary>externally preallocated data files may be ignored when allocating extents </summary>
                <type id="1" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14703&amp;avatarType=issuetype">Bug</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="milkie@mongodb.com">Eric Milkie</assignee>
                                    <reporter username="aaron">Aaron Staple</reporter>
                        <labels>
                    </labels>
                <created>Fri, 20 Apr 2012 21:45:04 +0000</created>
                <updated>Mon, 11 Jul 2016 18:33:17 +0000</updated>
                            <resolved>Thu, 7 Jun 2012 17:02:31 +0000</resolved>
                                                    <fixVersion>2.1.2</fixVersion>
                                    <component>Storage</component>
                                        <votes>0</votes>
                                    <watches>2</watches>
                                                                                                                <comments>
                            <comment id="125251" author="auto" created="Fri, 1 Jun 2012 20:09:19 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;login&apos;: u&apos;milkie&apos;, u&apos;name&apos;: u&apos;Eric Milkie&apos;, u&apos;email&apos;: u&apos;milkie@10gen.com&apos;}
&lt;p&gt;Message: removing invalid code that breaks &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-5670&quot; title=&quot;externally preallocated data files may be ignored when allocating extents &quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-5670&quot;&gt;&lt;del&gt;SERVER-5670&lt;/del&gt;&lt;/a&gt;&lt;br/&gt;
Branch: master&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/bc4b27c7a84e1172dc32809603c425abf9e97050&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/bc4b27c7a84e1172dc32809603c425abf9e97050&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="112182" author="aaron" created="Fri, 20 Apr 2012 22:20:07 +0000"  >&lt;p&gt;@eric There are multiple ways of fixing this specific issue.  For example we could alternatively modify openExistingFiles() &amp;#8211; and in fact it seems this has already been done in 2.1 and the issue may have been fixed there as a result.  It also makes sense to me that the size checks for existing and new files should be consistent.&lt;/p&gt;</comment>
                            <comment id="112176" author="thorn.roby@harlandfs.com" created="Fri, 20 Apr 2012 22:05:02 +0000"  >&lt;p&gt;I was about to rebuild our current production server using the new architecture described in CS-2838, which involves preallocating a large set of 2GB datafiles. I have been using the file size that matches datafiles created by mongod normally (2146435072), using dd with a single block of this size from /dev/zero (I settled on this after having some problems I don&apos;t remember exactly, when I used a file size computed as an exact 2GiB, which is slightly larger than this number). Does the scenario described here imply that I should use a slightly larger (maybe 8192) size to allow room for the file header? Or should I just hold off until you do some more investigation of the issue? Currently our production server is running well, as is the process of copying the data into the new server which is to become the replacement production server, so I&apos;m under no particular pressure to go ahead with the cutover if it is likely that the datafile preallocation problem might be better understood sometime in the next week or so.&lt;/p&gt;</comment>
                            <comment id="112171" author="milkie" created="Fri, 20 Apr 2012 21:56:47 +0000"  >&lt;p&gt;So from what you&apos;re saying, it sounds like the issue is that the Extent max size should not be the same as the max file size, due to the extra space taken up by a file header?&lt;br/&gt;
Or rather, that the check for extent space in a new file is different than the check for space in an existing file (and to fix this, we should make them the same).&lt;/p&gt;</comment>
                    </comments>
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            <issuekey id="40100">SERVER-5976</issuekey>
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