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<p style="margin-top:0;margin-bottom:0">Presently I'm experimenting with the following:</p>
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</p>
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<div>/etc/zfs/vdev_id.conf</div>
<div>alias ost01d1shasl00 /dev/disk/by-id/dm-uuid-mpath-35000cca26b825d6c</div>
<div>alias ost01d2shasl01 /dev/disk/by-id/dm-uuid-mpath-35000cca26b860178</div>
<div>alias ost01d3shasl02 /dev/disk/by-id/dm-uuid-mpath-35000cca26c1e2cb4</div>
<div>alias ost01d4shasl03 /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. 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>
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</p>
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</p>
I read on <a href="http://wiki.lustre.org/ZFS_OSD_Hardware_Considerations" class="OWAAutoLink" id="LPlnk187229">http://wiki.lustre.org/ZFS_OSD_Hardware_Considerations</a> that
<div><br>
</div>
<div>"<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 </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;"> that
enables failover-only capability."</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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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> lustre-discuss <lustre-discuss-bounces@lists.lustre.org> on behalf of lustre-discuss-request@lists.lustre.org <lustre-discuss-request@lists.lustre.org><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>
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1. Enable multipath for existing Lustre OST with ZFS backend<br>
(Tung-Han Hsieh)<br>
<br>
<br>
----------------------------------------------------------------------<br>
<br>
Message: 1<br>
Date: Fri, 10 May 2019 03:25:52 +0800<br>
From: Tung-Han Hsieh <thhsieh@twcp1.phys.ntu.edu.tw><br>
To: lustre-discuss@lists.lustre.org<br>
Subject: [lustre-discuss] Enable multipath for existing Lustre OST<br>
with ZFS backend<br>
Message-ID: <20190509192551.GA5793@twcp1.phys.ntu.edu.tw><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] disk IFT DS 1000 Series 661J /dev/sdb /dev/sg4<br>
[6:0:0:0] disk IFT DS 1000 Series 661J /dev/sdc /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=<host> --index=0 \<br>
--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 "chome_ost/ost" 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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