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<p>Here's an article explaining how dht works. The hash maps are
per-directory.<br>
</p>
<p><a class="moz-txt-link-freetext" href="https://joejulian.name/blog/dht-misses-are-expensive/">https://joejulian.name/blog/dht-misses-are-expensive/</a><br>
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<div class="moz-cite-prefix">On 11/08/2016 11:04 AM, Ankireddypalle
Reddy wrote:<br>
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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"> I am trying to make sense of the
hash values that get assigned/used by DHT.<o:p></o:p></p>
<p class="MsoNormal"> /brick1/vol and /brick2/vol are the
directories that are being used as bricks in a distributed
replicated volume.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">[root@glusterhackervm3 glus]# getfattr -n
trusted.glusterfs.dht -e hex /brick1/vol<o:p></o:p></p>
<p class="MsoNormal">getfattr: Removing leading '/' from
absolute path names<o:p></o:p></p>
<p class="MsoNormal"># file: brick1/vol<o:p></o:p></p>
<p class="MsoNormal">trusted.glusterfs.dht=0x0000000100000000000000007ffffde1<o:p></o:p></p>
<p class="MsoNormal">This means that any file gets hashed to a
value from 0x00 to 0x7ffffde1 gets stored on this brick.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">[root@glusterhackervm3 glus]# getfattr -n
trusted.glusterfs.dht -e hex /brick2/vol<o:p></o:p></p>
<p class="MsoNormal">getfattr: Removing leading '/' from
absolute path names<o:p></o:p></p>
<p class="MsoNormal"># file: brick2/vol<o:p></o:p></p>
<p class="MsoNormal">trusted.glusterfs.dht=0x00000001000000007ffffde2ffffffff
<o:p></o:p></p>
<p class="MsoNormal">This means that any file that’s hashed to a
value from 0x7ffffde2 to 0xffffffff gets stored on this brick.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">What is confusing is the dht values that
are shown for the directories inside these brick directories.
What do the dht values associated with the sub directories
signify.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">[root@glusterhackervm3 glus]# getfattr -n
trusted.glusterfs.dht -e hex /brick2/vol/d/<o:p></o:p></p>
<p class="MsoNormal">getfattr: Removing leading '/' from
absolute path names<o:p></o:p></p>
<p class="MsoNormal"># file: brick2/vol/d/<o:p></o:p></p>
<p class="MsoNormal">trusted.glusterfs.dht=0x0000000100000000000000007ffffffe<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">[root@glusterhackervm3 glus]# getfattr -n
trusted.glusterfs.dht -e hex /brick2/vol/d/e<o:p></o:p></p>
<p class="MsoNormal">getfattr: Removing leading '/' from
absolute path names<o:p></o:p></p>
<p class="MsoNormal"># file: brick2/vol/d/e<o:p></o:p></p>
<p class="MsoNormal">trusted.glusterfs.dht=0x0000000100000000000000007ffffffe<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">[root@glusterhackervm3 glus]# getfattr -n
trusted.glusterfs.dht -e hex /brick2/vol/d/f<o:p></o:p></p>
<p class="MsoNormal">getfattr: Removing leading '/' from
absolute path names<o:p></o:p></p>
<p class="MsoNormal"># file: brick2/vol/d/f<o:p></o:p></p>
<p class="MsoNormal">trusted.glusterfs.dht=0x00000001000000007fffffffffffffff<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks and Regards,<o:p></o:p></p>
<p class="MsoNormal">Ram<o:p></o:p></p>
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