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<p>This looks like <a href="https://jira.hpdd.intel.com/browse/LU-4257" class="x_OWAAutoLink" id="LPlnk876793">https://jira.hpdd.intel.com/browse/LU-4257</a>. (I'll let you read the details there.)<br>
<br>
That patch only went in a few months ago, so it's not in any released version yet.</p>
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<p>- Patrick</p>
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<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> lustre-discuss <lustre-discuss-bounces@lists.lustre.org> on behalf of Hans Henrik Happe <happe@nbi.ku.dk><br>
<b>Sent:</b> Sunday, October 2, 2016 7:54:14 AM<br>
<b>To:</b> lustre-discuss<br>
<b>Subject:</b> [lustre-discuss] Small sequential reads on cached file are slow</font>
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<div class="PlainText">Hi,<br>
<br>
While testing small sequential reads I noticed that Lustre is more than <br>
10 times slower than local fs when reading cached data. So basically no <br>
network I/O to OSSes. I wanted to check if readahead was working for <br>
this small I/O case, but it seems that cached case isn't.<br>
<br>
The client is running Lustre 2.8 and CentOS 6.8.<br>
<br>
Lustre:<br>
<br>
$ dd if=file of=/dev/null bs=512<br>
2097152+0 records in<br>
2097152+0 records out<br>
1073741824 bytes (1.1 GB) copied, 20.5081 s, 52.4 MB/s<br>
<br>
$ dd if=file of=/dev/null bs=4k<br>
262144+0 records in<br>
262144+0 records out<br>
1073741824 bytes (1.1 GB) copied, 2.91177 s, 369 MB/s<br>
<br>
$ dd if=file of=/dev/null bs=1M<br>
1024+0 records in<br>
1024+0 records out<br>
1073741824 bytes (1.1 GB) copied, 0.160732 s, 6.7 GB/s<br>
<br>
Local fs:<br>
<br>
$ dd if=/tmp/file of=/dev/null bs=512<br>
2097152+0 records in<br>
2097152+0 records out<br>
1073741824 bytes (1.1 GB) copied, 1.56432 s, 686 MB/s<br>
<br>
$ dd if=/tmp/file of=/dev/null bs=4k<br>
262144+0 records in<br>
262144+0 records out<br>
1073741824 bytes (1.1 GB) copied, 0.275451 s, 3.9 GB/s<br>
<br>
$ dd if=/tmp/file of=/dev/null bs=1M<br>
1024+0 records in<br>
1024+0 records out<br>
1073741824 bytes (1.1 GB) copied, 0.148798 s, 7.2 GB/s<br>
<br>
<br>
Is this a known issue?<br>
<br>
Cheers,<br>
Hans Henrik Happe<br>
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