[Beowulf] GPFS and failed metadata NSD

Bogdan Costescu bcostescu at gmail.com
Fri May 19 01:57:21 PDT 2017


Hello John,

I'm quite curious to know what was the thinking behind taking a
scratch filesystem down for so long, i.e. you wrote to the list on
29.04 and likely you experienced the problem some days before, and you
expect the image from the recovery company to reach you no sooner than
beginning of June, so a downtime of 6+ weeks? Is there some really
precious data stored there? Did you do some kind of costs analysis
comparing recovery costs with recomputing the data? Your description:

"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."

fits one of our large filesystems too :) The software side (BeeGFS)
has been resilient in the face of hardware failures until now, but I'm
worried about an extended hardware failure (i.e. several disks failing
at the same time) which would take some part of the data with them...

Cheers,
Bogdan

On Fri, May 19, 2017 at 9:39 AM, John Hanks <griznog at gmail.com> wrote:
> Thanks Arif, I'm signed up there now.
>
> As a general update, the most recently failed disk of the pair is at a data
> recovery company who thinks they can recover a workable image from it. We
> should have that back in two or three weeks and will try to use it to
> recover the filesystem.
>
> jbh
>
> On Thu, May 18, 2017 at 5:21 PM Arif Ali <mail at arif-ali.co.uk> wrote:
>>
>> Hi John,
>>
>> I would recommend joining up at spectrumscale.org mailing list, where you
>> will find very good experts from the HPC industry who know GPFS well,
>> including, Vendors, users and integrators. More specifically, you'll you'll
>> find gpfs developers on there. Maybe someone on that list can help out
>>
>> More direct link to the mailing list, here,
>> https://www.spectrumscale.org:10000/virtualmin-mailman/unauthenticated/listinfo.cgi/gpfsug-discuss/
>>
>>
>> On 29/04/2017 08:00, John Hanks wrote:
>>
>> 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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>>
>> --
>> regards,
>>
>> Arif Ali
>> Mob: +447970148122
>>
>> _______________________________________________
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>
> --
> ‘[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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