[gpfsug-discuss] Lost disks

[Uwe Falke]

gpfsug-discuss-bounces at spectrumscale.org wrote on 07/27/2017 05:09:31 PM:

> From: Jonathan Buzzard <jonathan.buzzard at strath.ac.uk>
> To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
> Date: 07/27/2017 05:09 PM
> Subject: Re: [gpfsug-discuss] Lost disks
> Sent by: gpfsug-discuss-bounces at spectrumscale.org

> 
> On Thu, 2017-07-27 at 16:18 +0200, Uwe Falke wrote:
> 
> > "Just doing something" makes things worse usually. Whether a 3rd
> > party tool knows how to handle GPFS NSDs can be doubted (as long as it
> > is not dedicated to that purpose). 
> 
> It might usually, but IBM have *ALREADY* given up in this case and told
> the customer their data is toast. Under these circumstances other than
> wasting time that could have been spent profitably on a restore it is
> *IMPOSSIBLE* to make the situation worse.
SCNR: It is always possible to make things worse.
However, of course, if the efforts to do research on that system appear 
too expensive compared to the possible gain, then it is wise to give up 
and restore data from backup to a new file system. 

> 
> [SNIP]
> 
> > It seems not a bad idea to set aside the NSD headers of your NSDs  in 
a 
> > back up :-)
> > And also now: Before amending any blocks on your disks, save them!
> > 
> 
> It's called NSD v2 descriptor format, so rather than use raw disks they
> are in a GPT partition, and for good measure a backup copy is stored at
> the end of the disk too.
> 
> Personally if I had any v1 NSD's in a file system I would have a plan
> for a series of mmdeldisk/mmcrnsd/mmadddisk to get them all to v2 sooner
> rather than later.

Yep, but I suppose the gone NSDs were v1. 
Then, there might be some restrictions blocking the move from NSDv1 to 
NSDv2 (old FS level still req.ed, or just the hugeness of a file system).
And you never know, if some tool runs wild due to logical failures it 
overwrites all GPT copies on a disk and you're lost again (but of course 
NSDv2 has been a tremendous step ahead).

 
Mit freundlichen Grüßen / Kind regards

 
Dr. Uwe Falke
 
IT Specialist
High Performance Computing Services / Integrated Technology Services / 
Data Center Services
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