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<div class="moz-cite-prefix">On 02.07.2015 05:59, <a class="moz-txt-link-abbreviated" href="mailto:Prakrati.Agrawal@shell.com">
Prakrati.Agrawal@shell.com</a> wrote:<br>
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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have two very basic doubts. <o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><span style="mso-list:Ignore">1.<span style="font:7.0pt
"Times New Roman"">
</span></span><!--[endif]-->If I have only one process writing to multiple OSTs, is it still a parallel write or does it become sequential as only one process is writing?</p>
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In principle it should still be parallel, but performance depends on many factors, like e.g. the access patterns and client cache settings.<br>
<blockquote cite="mid:1D5DCCB7C9001340A0A1AAAC50B856713D200C71@wybcvl-s-53404.europe.shell.com" type="cite">
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<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><span style="mso-list:Ignore">2.<span style="font:7.0pt
"Times New Roman"">
</span></span><!--[endif]-->Does MPI communication fabric interferes with file I/O?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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Performance-wise certainly. Concerning correctness, no. Many people are doing that without problems.<br>
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<p class="MsoNormal">I have a basic doubt:<o:p></o:p></p>
<p class="MsoNormal">If I have a directory whose stripe size is default and stripe count is set to 1. I have thousand files in that directory.<o:p></o:p></p>
<p class="MsoNormal">Total number of OSTs in my Lustre file system is say 8. Then how are those thousand files written to the OSTs?<o:p></o:p></p>
<p class="MsoNormal">Is it that first one OST is filled up with as many files as possible and then next OST is targeted or is it like file 1 to OST 1, file 2 to OST 2 and so on and then it comes back from file 13 to OST1.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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If the stripe index of the directory is set to -1, then the files are distributed round-robin to the OSTs.<br>
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