[Beowulf] GPFS and failed metadata NSD

[John Hanks]

Hi,

I'm not getting much useful vendor information so I thought I'd ask here in
the hopes that a GPFS expert can offer some advice. We have a GPFS system
which has the following disk config:

[root at grsnas01 ~]# mmlsdisk grsnas_data
disk         driver   sector     failure holds    holds
       storage
name         type       size       group metadata data  status
 availability pool
------------ -------- ------ ----------- -------- ----- -------------
------------ ------------
SAS_NSD_00   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_01   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_02   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_03   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_04   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_05   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_06   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_07   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_08   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_09   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_10   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_11   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_12   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_13   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_14   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_15   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_16   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_17   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_18   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_19   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_20   nsd         512         100 No       Yes   ready         up
        system
SAS_NSD_21   nsd         512         100 No       Yes   ready         up
        system
SSD_NSD_23   nsd         512         200 Yes      No    ready         up
        system
SSD_NSD_24   nsd         512         200 Yes      No    ready         up
        system
SSD_NSD_25   nsd         512         200 Yes      No    to be emptied down
        system
SSD_NSD_26   nsd         512         200 Yes      No    ready         up
        system

SSD_NSD_25 is a mirror in which both drives have failed due to a series of
unfortunate events and will not be coming back. From the GPFS
troubleshooting guide it appears that my only alternative is to run

mmdeldisk grsnas_data  SSD_NSD_25 -p

around which the documentation also warns is irreversible, the sky is
likely to fall, dogs and cats sleeping together, etc. But at this point I'm
already in an irreversible situation. Of course this is a scratch
filesystem, of course people were warned repeatedly about the risk of using
a scratch filesystem that is not backed up and of course many ignored that.
I'd like to recover as much as possible here. Can anyone confirm/reject
that deleting this disk is the best way forward or if there are other
alternatives to recovering data from GPFS in this situation?

Any input is appreciated. Adding salt to the wound is that until a few
months ago I had a complete copy of this filesystem that I had made onto
some new storage as a burn-in test but then removed as that storage was
consumed... As they say, sometimes you eat the bear, and sometimes, well,
the bear eats you.

Thanks,

jbh

(Naively calculated probability of these two disks failing close together
in this array: 0.00001758. I never get this lucky when buying lottery
tickets.)
-- 
‘[A] talent for following the ways of yesterday, is not sufficient to
improve the world of today.’
 - King Wu-Ling, ruler of the Zhao state in northern China, 307 BC
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