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List:       lustre-discuss
Subject:    Re: [lustre-discuss] lustre-discuss Digest, Vol 158, Issue 10
From:       Kurt Strosahl <strosahl () jlab ! org>
Date:       2019-05-09 20:38:42
Message-ID: BN8PR09MB35702233D2D13D07283B2494A7330 () BN8PR09MB3570 ! namprd09 ! prod ! outlook ! com
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Presently I'm experimenting with the following:


/etc/zfs/vdev_id.conf
alias ost01d1shasl00  /dev/disk/by-id/dm-uuid-mpath-35000cca26b825d6c
alias ost01d2shasl01  /dev/disk/by-id/dm-uuid-mpath-35000cca26b860178
alias ost01d3shasl02  /dev/disk/by-id/dm-uuid-mpath-35000cca26c1e2cb4
alias ost01d4shasl03  /dev/disk/by-id/dm-uuid-mpath-35000cca2680a8280


and using that to make sure that the disks have persistent names across reboots.  I \
still need to test pulling out one of the SAS cables to make sure that the \
multipathing works, and test replacing a disk.



I read on http://wiki.lustre.org/ZFS_OSD_Hardware_Considerations that

"The configuration of the device multi-mapper service is quite complex and can affect \
the performance characteristics of the solution. In some cases, JBODs can exhibit bad \
behavior from using load-balanced IO balancing, when in fact all the requests for a \
disk are expected to arrive from a single interface. For this reason, when working \
with JBODS it is recommended to use the path_grouping_policy that enables \
failover-only capability."

so I presently set my systems to failover mode.

w/r,
Kurt



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Subject: lustre-discuss Digest, Vol 158, Issue 10

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Today's Topics:

   1. Enable multipath for existing Lustre OST with ZFS backend
      (Tung-Han Hsieh)


----------------------------------------------------------------------

Message: 1
Date: Fri, 10 May 2019 03:25:52 +0800
From: Tung-Han Hsieh <thhsieh@twcp1.phys.ntu.edu.tw>
To: lustre-discuss@lists.lustre.org
Subject: [lustre-discuss] Enable multipath for existing Lustre OST
        with ZFS backend
Message-ID: <20190509192551.GA5793@twcp1.phys.ntu.edu.tw>
Content-Type: text/plain; charset=big5

Greetings,

Recently we have a new storage device. It has dual RAID controllers
with two fibre connections to the file server which map the LUM of
the storage to the server:

# lsscsi -g
[5:0:0:0]    disk    IFT      DS 1000 Series   661J  /dev/sdb   /dev/sg4
[6:0:0:0]    disk    IFT      DS 1000 Series   661J  /dev/sdc   /dev/sg6

# /lib/udev/scsi_id -g -u /dev/sdb
3600d02310009ff8750249f7e31c5fd86

# /lib/udev/scsi_id -g -u /dev/sdc
3600d02310009ff8750249f7e31c5fd86

So /dev/sdb and /dev/sdc are actually the same LUM of the storage.

We have created the Lustre OST with ZFS backend on /dev/sdb:

# mkfs.lustre --ost --fsname chome --mgsnode=<host> --index=0 \
              --backfstype=zfs chome_ost/ost /dev/sdb

It works fine. But soon after that, I was told that I should setup
multipath to take the advantage of dual fibre channel for load
balance and HA. I am wondering whether it is too late or not because
we already have data of Lustre file system running on it.

I read the documents of multipath. It seems that after setting
multipath, both /dev/sdb and /dev/sdc are re-mapped to, say,
/dev/mapper/mpath0. The existing data is probably not affacted.
What we need to do is just to replace the device name /dev/sdb
by /dev/mapper/mpath0 (please correct me if I am wrong). So the
problem seems leading to ZFS. Now my OST pool "chome_ost/ost" was
created on /dev/sdb. Could we replace the pool device name to
/dev/mapper/mpath0 ?

Thanks very much for you suggestions in advance :)

Best Regards,

T.H.Hsieh


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<style type="text/css" style="display:none;"><!-- P {margin-top:0;margin-bottom:0;} \
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<div id="divtagdefaultwrapper" \
style="font-size:12pt;color:#000000;font-family:Calibri,Helvetica,sans-serif;" \
dir="ltr"> <p style="margin-top:0;margin-bottom:0">Presently I'm experimenting with \
the following:</p> <p style="margin-top:0;margin-bottom:0"><br>
</p>
<p style="margin-top:0;margin-bottom:0"></p>
<div>/etc/zfs/vdev_id.conf</div>
<div>alias ost01d1shasl00&nbsp; /dev/disk/by-id/dm-uuid-mpath-35000cca26b825d6c</div>
<div>alias ost01d2shasl01&nbsp; /dev/disk/by-id/dm-uuid-mpath-35000cca26b860178</div>
<div>alias ost01d3shasl02&nbsp; /dev/disk/by-id/dm-uuid-mpath-35000cca26c1e2cb4</div>
<div>alias ost01d4shasl03&nbsp; /dev/disk/by-id/dm-uuid-mpath-35000cca2680a8280</div>
<br>
<p></p>
<p style="margin-top:0;margin-bottom:0">and using that to make sure that the disks \
have persistent names across reboots.&nbsp; I still need to test pulling out one of \
the SAS cables to make sure that the multipathing works, and test replacing a \
disk.</p> <p style="margin-top:0;margin-bottom:0"><br>
</p>
<p style="margin-top:0;margin-bottom:0"><br>
</p>
I read on&nbsp;<a href="http://wiki.lustre.org/ZFS_OSD_Hardware_Considerations" \
class="OWAAutoLink" id="LPlnk187229">http://wiki.lustre.org/ZFS_OSD_Hardware_Considerations</a>&nbsp;that
 <div><br>
</div>
<div>&quot;<span style="color: rgb(34, 34, 34); font-family: sans-serif; font-size: \
14px;">The configuration of the device multi-mapper service is quite complex and can \
affect the performance characteristics of the solution. In some cases, JBODs can \
exhibit bad  behavior from using load-balanced IO balancing, when in fact all the \
requests for a disk are expected to arrive from a single interface. For this reason, \
when working with JBODS it is recommended to use the&nbsp;</span><code \
style="font-family: monospace, Courier; background-color: rgb(248, 249, 250); border: \
1px solid rgb(234, 236, 240); border-radius: 2px; padding: 1px 4px; font-size: \
14px;">path_grouping_policy</code><span style="color: rgb(34, 34, 34); font-family: \
sans-serif; font-size: 14px;">&nbsp;that  enables failover-only \
capability.&quot;</span></div> <div><font color="#222222" face="sans-serif"><span \
style="font-size: 14px;"><br> </span></font></div>
<div><span style="color: rgb(34, 34, 34); font-family: sans-serif; font-size: \
14px;"></span><font color="#222222" face="sans-serif"><span style="font-size: \
14px;">so I presently set my systems to failover mode.</span></font></div> <div><font \
color="#222222" face="sans-serif"><span style="font-size: 14px;"><br> \
</span></font></div> <div><font color="#222222" face="sans-serif"><span \
style="font-size: 14px;">w/r,</span></font></div> <div><font color="#222222" \
face="sans-serif"><span style="font-size: 14px;">Kurt<br> </span></font><br>
<br>
<br>
<div style="color: rgb(0, 0, 0);">
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&lt;lustre-discuss-request@lists.lustre.org&gt;<br> <b>Sent:</b> Thursday, May 9, \
2019 4:21 PM<br> <b>To:</b> lustre-discuss@lists.lustre.org<br>
<b>Subject:</b> lustre-discuss Digest, Vol 158, Issue 10</font>
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Today's Topics:<br>
<br>
&nbsp;&nbsp; 1. Enable multipath for existing Lustre OST with ZFS backend<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (Tung-Han Hsieh)<br>
<br>
<br>
----------------------------------------------------------------------<br>
<br>
Message: 1<br>
Date: Fri, 10 May 2019 03:25:52 &#43;0800<br>
From: Tung-Han Hsieh &lt;thhsieh@twcp1.phys.ntu.edu.tw&gt;<br>
To: lustre-discuss@lists.lustre.org<br>
Subject: [lustre-discuss] Enable multipath for existing Lustre OST<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; with ZFS backend<br>
Message-ID: &lt;20190509192551.GA5793@twcp1.phys.ntu.edu.tw&gt;<br>
Content-Type: text/plain; charset=big5<br>
<br>
Greetings,<br>
<br>
Recently we have a new storage device. It has dual RAID controllers<br>
with two fibre connections to the file server which map the LUM of<br>
the storage to the server:<br>
<br>
# lsscsi -g<br>
[5:0:0:0]&nbsp;&nbsp;&nbsp; disk&nbsp;&nbsp;&nbsp; IFT&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \
DS 1000 Series&nbsp;&nbsp; 661J&nbsp; /dev/sdb&nbsp;&nbsp; /dev/sg4<br> \
[6:0:0:0]&nbsp;&nbsp;&nbsp; disk&nbsp;&nbsp;&nbsp; IFT&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \
DS 1000 Series&nbsp;&nbsp; 661J&nbsp; /dev/sdc&nbsp;&nbsp; /dev/sg6<br> <br>
# /lib/udev/scsi_id -g -u /dev/sdb<br>
3600d02310009ff8750249f7e31c5fd86<br>
<br>
# /lib/udev/scsi_id -g -u /dev/sdc<br>
3600d02310009ff8750249f7e31c5fd86<br>
<br>
So /dev/sdb and /dev/sdc are actually the same LUM of the storage.<br>
<br>
We have created the Lustre OST with ZFS backend on /dev/sdb:<br>
<br>
# mkfs.lustre --ost --fsname chome --mgsnode=&lt;host&gt; --index=0 \<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \
--backfstype=zfs chome_ost/ost /dev/sdb<br> <br>
It works fine. But soon after that, I was told that I should setup<br>
multipath to take the advantage of dual fibre channel for load<br>
balance and HA. I am wondering whether it is too late or not because<br>
we already have data of Lustre file system running on it.<br>
<br>
I read the documents of multipath. It seems that after setting<br>
multipath, both /dev/sdb and /dev/sdc are re-mapped to, say,<br>
/dev/mapper/mpath0. The existing data is probably not affacted.<br>
What we need to do is just to replace the device name /dev/sdb<br>
by /dev/mapper/mpath0 (please correct me if I am wrong). So the<br>
problem seems leading to ZFS. Now my OST pool &quot;chome_ost/ost&quot; was<br>
created on /dev/sdb. Could we replace the pool device name to<br>
/dev/mapper/mpath0 ?<br>
<br>
Thanks very much for you suggestions in advance :)<br>
<br>
Best Regards,<br>
<br>
T.H.Hsieh<br>
<br>
<br>
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