[gpfsug-discuss] Can't take snapshots while re-striping

Peter Childs p.childs at qmul.ac.uk
Thu Oct 18 16:32:43 BST 2018


We've just added 9 raid volumes to our main storage, (5 Raid6 arrays
for data and 4 Raid1 arrays for metadata)

We are now attempting to rebalance and our data around all the volumes.

We started with the meta-data doing a "mmrestripe -r" as we'd changed
the failure groups to on our meta-data disks and wanted to ensure we
had all our metadata on known good ssd. No issues, here we could take
snapshots and I even tested it. (New SSD on new failure group and move
all old SSD to the same failure group)

We're now doing a "mmrestripe -b" to rebalance the data accross all 21
Volumes however when we attempt to take a snapshot, as we do every
night at 11pm it fails with  

sudo /usr/lpp/mmfs/bin/mmcrsnapshot home test
Flushing dirty data for snapshot :test...
Quiescing all file system operations.
Unable to quiesce all nodes; some processes are busy or holding
required resources.
mmcrsnapshot: Command failed. Examine previous error messages to
determine cause.

Are you meant to be able to take snapshots while re-striping or not? 

I know a rebalance of the data is probably unnecessary, but we'd like
to get the best possible speed out of the system, and we also kind of
like balance.

Thanks


-- 
Peter Childs
ITS Research Storage
Queen Mary, University of London



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