[gpfsug-discuss] How to use RHEL 7 mdadm NVMe devices with Spectrum Scale 4.2.3.10?

Uwe Falke UWEFALKE at de.ibm.com
Fri Nov 16 09:35:25 GMT 2018


Hi, 

Having mentioned nsddevices, I do not know how Scale treats different 
device types differently, so generic would be a fine choice unless 
development tells you differently.
Currently known device types are listed in the comments of the script 
/usr/lpp/mmfs/bin/mmdevdiscover

 
Mit freundlichen Grüßen / Kind regards

 
Dr. Uwe Falke
 
IT Specialist
High Performance Computing Services / Integrated Technology Services / 
Data Center Services
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IBM Deutschland
Rathausstr. 7
09111 Chemnitz
Phone: +49 371 6978 2165
Mobile: +49 175 575 2877
E-Mail: uwefalke at de.ibm.com
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HRB 17122 




From:   Uwe Falke/Germany/IBM
To:     gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date:   16/11/2018 10:19
Subject:        Re: [gpfsug-discuss] How to use RHEL 7 mdadm NVMe devices 
with Spectrum   Scale 4.2.3.10?


Hi Lance, 
you might need to use 
/var/mmfs/etc/nsddevices
to tell GPFS about these devices (template in 
/usr/lpp/mmfs/samples/nsddevices.sample)


 
Mit freundlichen Grüßen / Kind regards

 
Dr. Uwe Falke
 
IT Specialist
High Performance Computing Services / Integrated Technology Services / 
Data Center Services
-------------------------------------------------------------------------------------------------------------------------------------------
IBM Deutschland
Rathausstr. 7
09111 Chemnitz
Phone: +49 371 6978 2165
Mobile: +49 175 575 2877
E-Mail: uwefalke at de.ibm.com
-------------------------------------------------------------------------------------------------------------------------------------------
IBM Deutschland Business & Technology Services GmbH / Geschäftsführung: 
Thomas Wolter, Sven Schooß
Sitz der Gesellschaft: Ehningen / Registergericht: Amtsgericht Stuttgart, 
HRB 17122 





From:   Lance Nakata <LNakata at SLAC.STANFORD.EDU>
To:     gpfsug-discuss at spectrumscale.org
Cc:     "Jon L. Bergman" <jonl at SLAC.STANFORD.EDU>
Date:   16/11/2018 04:14
Subject:        [gpfsug-discuss] How to use RHEL 7 mdadm NVMe devices with 
Spectrum        Scale 4.2.3.10?
Sent by:        gpfsug-discuss-bounces at spectrumscale.org



We have a Dell R740xd with 24 x 1TB NVMe SSDs in the internal slots. Since 
PERC
RAID cards don't see these devices, we are using mdadm software RAID to 
build
NSDs.  We took 12 NVMe SSDs and used mdadm to create a 10 + 1 + 1 hot 
spare RAID
5 stripe named /dev/md101.  We took the other 12 NVMe SSDs and created a 
similar
/dev/md102.

mmcrnsd worked without errors.  The problem is that Spectrum Scale does 
not see
the /dev/md10x devices as proper NSDs; the Device and Devtype columns are 
blank:

host2:~> sudo mmlsnsd -X

 Disk name    NSD volume ID      Device         Devtype  Node name  
Remarks
---------------------------------------------------------------------------------------------------
 nsd0001      864FD12858A36E79   /dev/sdb       generic 
host1.slac.stanford.edu server node
 nsd0002      864FD12858A36E7A   /dev/sdc       generic 
host1.slac.stanford.edu server node
 nsd0021      864FD1285956B0A7   /dev/sdd       generic 
host1.slac.stanford.edu server node
 nsd0251a     864FD1545BD0CCDF   /dev/dm-9      dmm 
host2.slac.stanford.edu server node
 nsd0251b     864FD1545BD0CCE0   /dev/dm-11     dmm 
host2.slac.stanford.edu server node
 nsd0252a     864FD1545BD0CCE1   /dev/dm-10     dmm 
host2.slac.stanford.edu server node
 nsd0252b     864FD1545BD0CCE2   /dev/dm-8      dmm 
host2.slac.stanford.edu server node
 nsd02nvme1   864FD1545BEC5D72   -              - host2.slac.stanford.edu 
(not found) server node
 nsd02nvme2   864FD1545BEC5D73   -              - host2.slac.stanford.edu 
(not found) server node

I know we can access the internal NVMe devices by their individual 
/dev/nvmeXX
paths, but non-ESS-based Spectrum Scale does not have built-in RAID
functionality.  Hence, the only option in that scenario is replication, 
which is
expensive and won't give us enough usable space.

Software Environment:
RHEL 7.6 with kernel 3.10.0-862.14.4.el7.x86_64
Spectrum Scale 4.2.3.10

Spectrum Scale Support has implied we can't use mdadm for NVMe devices. Is 
that
really true?  Does anyone use an mdadm-based NVMe config?  If so, did you 
have
to do some kind of customization to get it working?

Thank you,

Lance Nakata
SLAC National Accelerator Laboratory
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