[gpfsug-discuss] Using HAWC (write cache)

Simon Thompson (Research Computing - IT Services) S.J.Thompson at bham.ac.uk
Thu Aug 27 08:42:34 BST 2015


Hi Dean,

Thanks. I wasn't sure if the system.log disks on clients in the remote cluster would be "valid" as they are essentially NSDs in a different cluster from where the storage cluster would be, but it sounds like it is.

Now if I can just get it working ... Looking in mmfsfuncs:


  if [[ $diskUsage != "localCache" ]]

  then

    combinedList=${primaryAdminNodeList},${backupAdminNodeList}

    IFS=","

    for server in $combinedList

    do

      IFS="$IFS_sv"

      [[ -z $server ]] && continue


      $grep -q -e "^${server}$" $serverLicensedNodes > /dev/null 2>&1

      if [[ $? -ne 0 ]]

      then

        # The node does not have a server license.

        printErrorMsg 118 $mmcmd $server

        return 1

      fi

      IFS=","

    done  # end for server in ${primaryAdminNodeList},${backupAdminNodeList}

    IFS="$IFS_sv"

  fi  # end of if [[ $diskUsage != "localCache" ]]

So unless the NSD device usage=localCache, then it requires a server License when you try and create the NSD, but localCache cannot have a storage pool assigned.

I've opened a PMR with IBM.

Simon

From: Dean Hildebrand <dhildeb at us.ibm.com<mailto:dhildeb at us.ibm.com>>
Reply-To: gpfsug main discussion list <gpfsug-discuss at gpfsug.org<mailto:gpfsug-discuss at gpfsug.org>>
Date: Thursday, 27 August 2015 01:22
To: gpfsug main discussion list <gpfsug-discuss at gpfsug.org<mailto:gpfsug-discuss at gpfsug.org>>
Subject: Re: [gpfsug-discuss] Using HAWC (write cache)


Hi Simon,

HAWC leverages the System.log (or metadata pool if no special log pool is defined) pool.... so its independent of local or multi-cluster modes... small writes will be 'hardened' whereever those pools are defined for the file system.

Dean Hildebrand
IBM Master Inventor and Manager | Cloud Storage Software
IBM Almaden Research Center


[Inactive hide details for "Simon Thompson (Research Computing - IT Services)" ---08/26/2015 05:58:12 AM---Oh and one other ques]"Simon Thompson (Research Computing - IT Services)" ---08/26/2015 05:58:12 AM---Oh and one other question about HAWC, does it work when running multi-cluster? I.e. Can clients in a

From: "Simon Thompson (Research Computing - IT Services)" <S.J.Thompson at bham.ac.uk<mailto:S.J.Thompson at bham.ac.uk>>
To: gpfsug main discussion list <gpfsug-discuss at gpfsug.org<mailto:gpfsug-discuss at gpfsug.org>>
Date: 08/26/2015 05:58 AM
Subject: Re: [gpfsug-discuss] Using HAWC (write cache)
Sent by: gpfsug-discuss-bounces at gpfsug.org<mailto:gpfsug-discuss-bounces at gpfsug.org>

________________________________



Oh and one other question about HAWC, does it work when running
multi-cluster? I.e. Can clients in a remote cluster have HAWC devices?

Simon

On 26/08/2015 12:26, "Simon Thompson (Research Computing - IT Services)"
<S.J.Thompson at bham.ac.uk<mailto:S.J.Thompson at bham.ac.uk>> wrote:

>Hi,
>
>I was wondering if anyone knows how to configure HAWC which was added in
>the 4.1.1 release (this is the hardened write cache)
>(http://www-01.ibm.com/support/knowledgecenter/#!/STXKQY/411/com.ibm.spect
>r
>um.scale.v4r11.adv.doc/bl1adv_hawc_using.htm)
>
>In particular I'm interested in running it on my client systems which have
>SSDs fitted for LROC, I was planning to use a small amount of the LROC SSD
>for HAWC on our hypervisors as it buffers small IO writes, which sounds
>like what we want for running VMs which are doing small IO updates to the
>VM disk images stored on GPFS.
>
>The docs are a little lacking in detail of how you create NSD disks on
>clients, I've tried using:
>%nsd: device=sdb2
>  nsd=cl0901u17_hawc_sdb2
>  servers=cl0901u17
>  pool=system.log
>  failureGroup=90117
>
>(and also with usage=metadataOnly as well), however mmcrsnd -F tells me
>"mmcrnsd: Node cl0903u29.climb.cluster does not have a GPFS server license
>designation"
>
>
>Which is correct as its a client system, though HAWC is supposed to be
>able to run on client systems. I know for LROC you have to set
>usage=localCache, is there a new value for using HAWC?
>
>I'm also a little unclear about failureGroups for this. The docs suggest
>setting the HAWC to be replicated for client systems, so I guess that
>means putting each client node into its own failure group?
>
>Thanks
>
>Simon
>
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>gpfsug-discuss mailing list
>gpfsug-discuss at gpfsug.org
>http://gpfsug.org/mailman/listinfo/gpfsug-discuss

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