<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<!--[if !mso]><style>v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style><![endif]--><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
tt
{mso-style-priority:99;
font-family:"Courier New";}
p.msonormal0, li.msonormal0, div.msonormal0
{mso-style-name:msonormal;
mso-margin-top-alt:auto;
margin-right:0cm;
mso-margin-bottom-alt:auto;
margin-left:0cm;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
span.EmailStyle19
{mso-style-type:personal-reply;
font-family:"Calibri",sans-serif;
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:72.0pt 72.0pt 72.0pt 72.0pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="EN-GB" link="blue" vlink="purple">
<div class="WordSection1">
<p class="MsoNormal">OK we think we might have a reason for this.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We run iptables on some of our management function nodes, and we found that in some cases, our config management tool can cause a ‘systemctl restart iptables’ to occur (the rule ordering generation was non deterministic meaning it could
shuffle rules … we fixed that and made it reload rather than restart). Which takes a fraction of a second, but it appears that this is sufficient for GPFS to get into a state. What I didn’t mention before was that we could get it into a state where the only
way to recover was to shutdown the storage cluster and restart it.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’m not sure why normal expel and recovery doesn’t appear to work in this case, though we’re not 100% certain that its iptables restart. (we just have a very smoky gun at present). (I have a ticket with that question open).<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Maybe it’s a combination of having a default DROP policy on iptables as well - we have also switched to ACCEPT and added a DROP rule at the end of the ruleset which gives the same result.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Simon<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black"><gpfsug-discuss-bounces@spectrumscale.org> on behalf of "jlewars@us.ibm.com" <jlewars@us.ibm.com><br>
<b>Reply-To: </b>"gpfsug-discuss@spectrumscale.org" <gpfsug-discuss@spectrumscale.org><br>
<b>Date: </b>Thursday, 17 January 2019 at 14:31<br>
<b>To: </b>Tomer Perry <TOMP@il.ibm.com>, "gpfsug-discuss@spectrumscale.org" <gpfsug-discuss@spectrumscale.org><br>
<b>Cc: </b>Yong Ze Chen <yongzech@cn.ibm.com><br>
<b>Subject: </b>Re: [gpfsug-discuss] Node expels<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">></span><span style="font-size:10.0pt">They always appear to be to a specific type of hardware with the same Ethernet controller,
</span><br>
<br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">That makes me think you might be seeing packet loss that could require ring buffer tuning (the defaults and limits will differ with different ethernet adapters). </span><br>
<br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">The expel section in the slides on this page has been expanded to include a 'debugging expels section' (slides 19-20, which also reference ring buffer tuning):<br>
</span><a href="https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/General%20Parallel%20File%20System%20(GPFS)/page/DEBUG%20Expels/comment/7e4f9433-7ca3-430f-b40b-94777c507381"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/General%20Parallel%20File%20System%20(GPFS)/page/DEBUG%20Expels/comment/7e4f9433-7ca3-430f-b40b-94777c507381</span></a><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><br>
</span><br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">Regards,<br>
John Lewars <br>
Spectrum Scale Performance, IBM Poughkeepsie<br>
</span><br>
<br>
<br>
<br>
<span style="font-size:7.5pt;font-family:"Arial",sans-serif;color:#5F5F5F">From: </span><span style="font-size:7.5pt;font-family:"Arial",sans-serif">Tomer Perry/Israel/IBM</span><br>
<span style="font-size:7.5pt;font-family:"Arial",sans-serif;color:#5F5F5F">To: </span><span style="font-size:7.5pt;font-family:"Arial",sans-serif">gpfsug main discussion list <gpfsug-discuss@spectrumscale.org></span><br>
<span style="font-size:7.5pt;font-family:"Arial",sans-serif;color:#5F5F5F">Cc: </span><span style="font-size:7.5pt;font-family:"Arial",sans-serif">John Lewars/Poughkeepsie/IBM@IBMUS, Yong Ze Chen/China/IBM@IBMCN</span><br>
<span style="font-size:7.5pt;font-family:"Arial",sans-serif;color:#5F5F5F">Date: </span><span style="font-size:7.5pt;font-family:"Arial",sans-serif">01/17/2019 08:28 AM</span><br>
<span style="font-size:7.5pt;font-family:"Arial",sans-serif;color:#5F5F5F">Subject: </span><span style="font-size:7.5pt;font-family:"Arial",sans-serif">Re: [gpfsug-discuss] Node expels</span><o:p></o:p></p>
<div class="MsoNormal" align="center" style="text-align:center">
<hr size="0" width="100%" noshade="" style="color:#A0A0A0" align="center">
</div>
<p class="MsoNormal"><br>
<br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">Hi,</span><br>
<br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">I was asked to elaborate a bit ( thus also adding John and Yong Ze Chen).</span><br>
<br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">As written on the slide:</span><br>
<span style="font-size:12.0pt">One of the best ways to determine if a network layer problem is root cause for an expel is to look at the low-level socket details dumped in the ‘extra’ log data (mmfs dump all) saved as part of automatic data collection on Linux
GPFS nodes. </span><br>
<br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">So, the idea is that in expel situation, we dump the socket state from the OS ( you can see the same using 'ss -i' for example).</span><br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">In your example, it shows that the ca_state is 4, there are retransmits, high rto and all the point to a network problem.</span><br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">You can find more details here:
</span><a href="http://www.yonch.com/tech/linux-tcp-congestion-control-internals"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">http://www.yonch.com/tech/linux-tcp-congestion-control-internals</span></a><br>
<br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif"><br>
Regards,<br>
<br>
Tomer Perry<br>
Scalable I/O Development (Spectrum Scale)<br>
email: tomp@il.ibm.com<br>
1 Azrieli Center, Tel Aviv 67021, Israel<br>
Global Tel: +1 720 3422758<br>
Israel Tel: +972 3 9188625<br>
Mobile: +972 52 2554625<br>
</span><br>
<br>
<br>
<br>
<br>
<span style="font-size:7.5pt;font-family:"Arial",sans-serif;color:#5F5F5F">From: </span><span style="font-size:7.5pt;font-family:"Arial",sans-serif">"Tomer Perry" <TOMP@il.ibm.com></span><br>
<span style="font-size:7.5pt;font-family:"Arial",sans-serif;color:#5F5F5F">To: </span><span style="font-size:7.5pt;font-family:"Arial",sans-serif">gpfsug main discussion list <gpfsug-discuss@spectrumscale.org></span><br>
<span style="font-size:7.5pt;font-family:"Arial",sans-serif;color:#5F5F5F">Date: </span><span style="font-size:7.5pt;font-family:"Arial",sans-serif">17/01/2019 13:46</span><br>
<span style="font-size:7.5pt;font-family:"Arial",sans-serif;color:#5F5F5F">Subject: </span><span style="font-size:7.5pt;font-family:"Arial",sans-serif">Re: [gpfsug-discuss] Node expels</span><br>
<span style="font-size:7.5pt;font-family:"Arial",sans-serif;color:#5F5F5F">Sent by: </span><span style="font-size:7.5pt;font-family:"Arial",sans-serif">gpfsug-discuss-bounces@spectrumscale.org</span><o:p></o:p></p>
<div class="MsoNormal" align="center" style="text-align:center">
<hr size="0" width="100%" noshade="" style="color:#A0A0A0" align="center">
</div>
<p class="MsoNormal"><br>
<br>
<br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">Simon,</span><span style="font-size:12.0pt"><br>
</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><br>
Take a look at </span><a href="http://files.gpfsug.org/presentations/2018/USA/Scale_Network_Flow-0.8.pdf"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">http://files.gpfsug.org/presentations/2018/USA/Scale_Network_Flow-0.8.pdf</span></a><span style="font-size:10.0pt;font-family:"Arial",sans-serif">slide
13.</span><span style="font-size:12.0pt"><br>
</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><br>
<br>
Regards,<br>
<br>
Tomer Perry<br>
Scalable I/O Development (Spectrum Scale)<br>
email: tomp@il.ibm.com<br>
1 Azrieli Center, Tel Aviv 67021, Israel<br>
Global Tel: +1 720 3422758<br>
Israel Tel: +972 3 9188625<br>
Mobile: +972 52 2554625</span><span style="font-size:12.0pt"><br>
<br>
<br>
<br>
</span><span style="font-size:7.5pt;font-family:"Arial",sans-serif;color:#5F5F5F"><br>
From: </span><span style="font-size:7.5pt;font-family:"Arial",sans-serif">Simon Thompson <S.J.Thompson@bham.ac.uk><span style="color:#5F5F5F"><br>
To: </span>"gpfsug-discuss@spectrumscale.org" <gpfsug-discuss@spectrumscale.org><span style="color:#5F5F5F"><br>
Date: </span>17/01/2019 13:35<span style="color:#5F5F5F"><br>
Subject: </span>[gpfsug-discuss] Node expels<span style="color:#5F5F5F"><br>
Sent by: </span>gpfsug-discuss-bounces@spectrumscale.org</span><o:p></o:p></p>
<div class="MsoNormal" align="center" style="text-align:center">
<hr size="0" width="100%" noshade="" style="color:#A0A0A0" align="center">
</div>
<p class="MsoNormal"><span style="font-size:12.0pt"><br>
<br>
</span><span style="font-size:10.0pt"><br>
We’ve recently been seeing quite a few node expels with messages of the form:<br>
<br>
2019-01-17_11:19:30.882+0000: [W] The TCP connection to IP address 10.20.0.58 proto-pg-pf01.bear.cluster <c0n236> (socket 153) state is unexpected: state=1 ca_state=4 snd_cwnd=1 snd_ssthresh=5 unacked=5 probes=0 backoff=7 retransmits=7 rto=26496000 rcv_ssthresh=102828
rtt=6729 rttvar=12066 sacked=0 retrans=1 reordering=3 lost=5<br>
2019-01-17_11:19:30.882+0000: [I] tscCheckTcpConn: Sending debug data collection request to node 10.20.0.58 proto-pg-pf01.bear.cluster<br>
2019-01-17_11:19:30.882+0000: Sending request to collect TCP debug data to proto-pg-pf01.bear.cluster localNode<br>
2019-01-17_11:19:30.882+0000: [I] Calling user exit script gpfsSendRequestToNodes: event sendRequestToNodes, Async command /usr/lpp/mmfs/bin/mmcommon.<br>
2019-01-17_11:24:52.611+0000: [E] Timed out in 300 seconds waiting for a commMsgCheckMessages reply from node 10.20.0.58 proto-pg-pf01.bear.cluster. Sending expel message.<br>
<br>
On the client node, we see messages of the form:<br>
<br>
2019-01-17_11:19:31.101+0000: [N] sdrServ: Received Tcp data collection request from 10.10.0.33<br>
2019-01-17_11:19:31.102+0000: [N] GPFS will attempt to collect Tcp debug data on this node.<br>
2019-01-17_11:24:52.838+0000: [N] sdrServ: Received expel data collection request from 10.10.0.33<br>
2019-01-17_11:24:52.838+0000: [N] GPFS will attempt to collect debug data on this node.<br>
2019-01-17_11:25:02.741+0000: [N] This node will be expelled from cluster rds.gpfs.servers due to expel msg from 10.10.12.41 (b<br>
ber-les-nsd01-data.bb2.cluster in rds.gpfs.server<br>
2019-01-17_11:25:03.160+0000: [N] sdrServ: Received expel data collection request from 10.20.0.56<br>
<br>
They always appear to be to a specific type of hardware with the same Ethernet controller, though the nodes are split across three data centres and we aren’t seeing link congestion on the links between them.<br>
<br>
On the node I listed above, it’s not actually doing anything either as the software on it is still being installed (i.e. it’s not doing GPFS or any other IO other than a couple of home directories).<br>
<br>
Any suggestions on what “(socket 153) state is unexpected” means?<br>
<br>
Thanks<br>
<br>
Simon<br>
<br>
</span><tt><span style="font-size:10.0pt">_______________________________________________</span></tt><span style="font-size:10.0pt;font-family:"Courier New""><br>
<tt>gpfsug-discuss mailing list</tt><br>
<tt>gpfsug-discuss at spectrumscale.org</tt></span><u><span style="font-size:12.0pt;color:blue"><br>
</span></u><a href="http://gpfsug.org/mailman/listinfo/gpfsug-discuss"><tt><span style="font-size:10.0pt">http://gpfsug.org/mailman/listinfo/gpfsug-discuss</span></tt></a><span style="font-size:12.0pt"><br>
<br>
<br>
</span><tt><span style="font-size:10.0pt">_______________________________________________</span></tt><span style="font-size:10.0pt;font-family:"Courier New""><br>
<tt>gpfsug-discuss mailing list</tt><br>
<tt>gpfsug-discuss at spectrumscale.org</tt><br>
</span><a href="http://gpfsug.org/mailman/listinfo/gpfsug-discuss"><tt><span style="font-size:10.0pt">http://gpfsug.org/mailman/listinfo/gpfsug-discuss</span></tt></a><span style="font-size:10.0pt;font-family:"Courier New""><br>
</span><br>
<br>
<br>
<br>
<br>
<o:p></o:p></p>
</div>
</body>
</html>