<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Mar 20, 2018 at 8:57 AM, Sam McLeod <span dir="ltr"><<a href="mailto:mailinglists@smcleod.net" target="_blank">mailinglists@smcleod.net</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: break-word;">Hi Raghavendra,<div><br></div><div><br></div><div><span class="gmail-"><div></div><blockquote type="cite"><div><font color="#000000">On 20 Mar 2018, at 1:55 pm, Raghavendra Gowdappa <<a href="mailto:rgowdapp@redhat.com" target="_blank">rgowdapp@redhat.com</a>> wrote:</font></div><div><div class="gmail_quote"><div><font color="#000000"><br></font></div><div><font color="#000000">Aggregating large number of small writes by write-behind into large writes has been merged on master:<br></font></div><div><a href="https://github.com/gluster/glusterfs/issues/364" target="_blank"><font color="#000000">https://github.com/gluster/<wbr>glusterfs/issues/364</font></a></div><div><font color="#000000"><br></font></div><div><font color="#000000">Would like to know whether it helps for this usecase. Note that its not part of any release yet. So you've to build and install from repo.</font></div></div></div></blockquote><div><br></div></span>Sounds interesting, not too keen to build packages at the moment but I've added myself as a watcher to that issue on Github and once it's in a 3.x release I'll try it and let you know.<span class="gmail-"><br><br><blockquote type="cite"><div><div class="gmail_quote"><div><font color="#000000">Another suggestion is to run tests with turning off option performance.write-behind-<wbr>trickling-writes.</font></div><div><font color="#000000"><br></font></div><div><font color="#000000"># gluster volume set <volname> performance.write-behind-<wbr>trickling-writes off<br></font></div><div><font color="#000000"><br></font></div><div><font color="#000000">A word of caution though is if your files are too small, these suggestions may not have much impact.</font></div></div></div></blockquote></span><div><div class="gmail_quote"><div><br></div><div>I'm looking for documentation on this option but all I could really find is in the source for write-behind.c:</div><div><br></div><div>if is enabled (which it is), do not hold back writes if there are no outstanding requests.</div></div></div></div></div></blockquote><div><br></div><div>Till recently this functionality though was available, couldn't be configured from cli. One could change this option by editing volume configuration file. However, now its configurable through cli:</div><div><br></div><div><a href="https://review.gluster.org/#/c/18719/">https://review.gluster.org/#/c/18719/</a><br></div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: break-word;"><div><div><div class="gmail_quote"><div><br></div><div><br></div><div>and a note on aggregate-size stating that </div><div><div><br></div><div><i>"aggregation won't happen if performance.write-behind-<wbr>trickling-writes is turned on"</i></div><div><br></div><div><br></div><div>What are the potentially negative performance impacts of disabling this?</div></div></div></div></div></div></blockquote><div><br></div><div>Even if aggregation option is turned off, write-behind has the capacity to aggregate till a size of 128KB. But, to completely make use of this in case of small write workloads write-behind has to wait for sometime so that there are enough number of write-requests to fill the capacity. With this option enabled, write-behind though aggregates existing requests, won't wait for future writes. This means descendant xlators of write-behind can see writes smaller than 128K. So, for a scenario where small number of large writes are preferred over large number of small sized writes, this can be a problem.<br></div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: break-word;"><span class="gmail-"><div><br><div>
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