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<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">Hi, Gluster expert,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">When we setup replicate volume with info like the below:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">Volume Name: test<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">Type: Replicate<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">Volume ID: 9373eba9-eb84-4618-a54c-f2837345daec<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">Status: Started<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">Snapshot Count: 0<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">Number of Bricks: 1 x (2 + 1) = 3<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">Transport-type: tcp<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">Bricks:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">Brick1: rcp:/trunk/brick/test1/sn0<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">Brick2: rcp:/trunk/brick/test1/sn1<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">Brick3: rcp:/trunk/brick/test1/sn2 (arbiter)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">If we run a performance test which could write a same file with multi-pthread in same time.(write different offset). The write performance drop a lots (about 60%-70% off
to the volume which no arbiter) <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">And when we study the source code, there is a function “afr_set_transaction_flock” in” afr-transaction.c”, <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">It will flock the entire file when arbiter_count is not zero, I suppose it is the root cause lead to performance drop.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">Now my question is:<o:p></o:p></span></p>
<p class="MsoListParagraph" style="margin-left:18.0pt;text-indent:-18.0pt;mso-list:l0 level1 lfo1">
<![if !supportLists]><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"><span style="mso-list:Ignore">1)<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">Why flock the entire file when arbiter is set on? Could you please share the detail why it will lead to split brain only to arbiter?<o:p></o:p></span></p>
<p class="MsoListParagraph" style="margin-left:18.0pt;text-indent:-18.0pt;mso-list:l0 level1 lfo1">
<![if !supportLists]><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"><span style="mso-list:Ignore">2)<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">If it is the root cause, and it really will lead to split-brain if not lock entire file, is there any solution to avoid performance drop for this mulit-write case?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">The following is attached source code for this function FYI:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">--------------------------------------------------------------------------------------<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">int afr_set_transaction_flock (xlator_t *this, afr_local_t *local)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">{<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> afr_internal_lock_t *int_lock = NULL;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> afr_private_t *priv = NULL;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> int_lock = &local->internal_lock;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> priv = this->private;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> if ((priv->arbiter_count || local->transaction.eager_lock_on ||<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> priv->full_lock) &&<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> local->transaction.type == AFR_DATA_TRANSACTION) {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> /*Lock entire file to avoid network split brains.*/<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> int_lock->flock.l_len = 0;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> int_lock->flock.l_start = 0;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> } else {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> int_lock->flock.l_len = local->transaction.len;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> int_lock->flock.l_start = local->transaction.start;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> int_lock->flock.l_type = F_WRLCK;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian"> return 0;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">}<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">------------------------------------------------------------------------------------<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">Thanks & Best Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:DengXian">George<o:p></o:p></span></p>
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