[lustre-discuss] Target names changing when mounting

[Drokin, Oleg]

I see.
Well, using those symlinks was certainly not expected when this code was written.
So I imagine avoid using them and perhaps use /dev/disk/by-uuid which should be more stable
in the face of writeconfs?

On Jul 31, 2015, at 2:36 PM, Andrus, Brian Contractor wrote:

> Oleg, 
> 
> When it changes the e2label, the links in /dev/disk/by-label get changed too.
> 
> 
> Brian Andrus
> ITACS/Research Computing
> Naval Postgraduate School
> Monterey, California
> voice: 831-656-6238
> 
> 
> 
> 
> -----Original Message-----
> From: Drokin, Oleg [mailto:oleg.drokin at intel.com] 
> Sent: Friday, July 31, 2015 11:31 AM
> To: Andrus, Brian Contractor
> Cc: lustre-discuss at lists.lustre.org
> Subject: Re: [lustre-discuss] Target names changing when mounting
> 
> Hello!
> 
> On Jul 31, 2015, at 2:08 PM, Andrus, Brian Contractor wrote:
> 
>> All,
>> 
>> I find this very confusing..
>> I created a new lustre filesystem (WORK2) by creating and MDT and a single OST.
>> When I first create them, the names shown for Target have different values from 'Read precious values' and 'Permanent disk data'
>> The difference is a hyphen '-' versus a colon ':'
> 
> This is internal bookkeeping to show target status:
> 
>        /* svname of the form lustre:OST1234 means never registered */
> 	rc = strlen(ldd->ldd_svname);
>        if (ldd->ldd_svname[rc - 8] == ':') {
>                ldd->ldd_svname[rc - 8] = '-';
>                ldd->ldd_flags |= LDD_F_VIRGIN;
>        } else if (ldd->ldd_svname[rc - 8] == '=') {
>                ldd->ldd_svname[rc - 8] = '-';
>                ldd->ldd_flags |= LDD_F_WRITECONF;
>        }
> 
>> 
>>   Read previous values:
>> Target:     WORK2-MDT0000
>> 
>>   Permanent disk data:
>> Target:     WORK2:MDT0000
>> 
>> The ext2 label on the disk matches the Permanent disk data.
>> BUT....
>> When I mount it (mount -t lustre) the Permanent disk data changes to use a colon and the e2label changes....
>>   Read previous values:
>> Target:     WORK2-MDT0000
>> 
>>   Permanent disk data:
>> Target:     WORK2-MDT0000
>> 
>> THEN...
>> If I do a tunefs.lustre --writeconf , it changes the Permanent disk data AND the e2label to use an equal '=' sign:
>> 
>>   Read previous values:
>> Target:     WORK2-MDT0000
>> 
>>   Permanent disk data:
>> Target:     WORK2=MDT0000
>> 
>> Next time I mount it changes it back to the hyphen '-' So.. What the 
>> heck???
> 
> Matches the code so far.
> 
>> Now the problem/annoyance is the fact that this changes links in /dev...
> 
> What links? This is internal lustre target name, your block device name should still stay the same as it was.
> 
>> And an equal sign '=' is NOT a happy character for device names... I am 
>> also highly suspicious this affects some of the mappings in the MGS 
>> and MDT which is causing great grief...
> 
> Should not, really, since this is expected and we treat those changes as meaningful to indicate the target status.
> 
> Bye,
>    Oleg
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