[gpfsug-discuss] Using HAWC (write cache)

[Simon Thompson (Research Computing - IT Services)]

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.spectr
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