* [Lustre-devel] mounting a device twice
@ 2013-07-24 17:26 Michael Kluge
2013-07-25 2:39 ` Dilger, Andreas
0 siblings, 1 reply; 3+ messages in thread
From: Michael Kluge @ 2013-07-24 17:26 UTC (permalink / raw)
To: lustre-devel
Hi list,
can I mount a device mounted as lustre a second time as ldiskfs or would
MMP protect me from doing this?
Regards, Michael
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* [Lustre-devel] mounting a device twice
2013-07-24 17:26 [Lustre-devel] mounting a device twice Michael Kluge
@ 2013-07-25 2:39 ` Dilger, Andreas
2013-07-25 5:13 ` Michael Kluge
0 siblings, 1 reply; 3+ messages in thread
From: Dilger, Andreas @ 2013-07-25 2:39 UTC (permalink / raw)
To: lustre-devel
You can do this because the kernel is not actually mounting the block device twice. Lustre is mounting the block device internally as type ldiskfs and the second mount will be like a bind mount of the same filesystem root tree.
I do this on my local filesystem for quick debugging, but it isn't strictly safe on an active filesystem because modifications can render the Lustre and on disk state inconsistent.
Cheers, Andreas
On 2013-07-24, at 11:27, "Michael Kluge" <michael.kluge@tu-dresden.de> wrote:
> Hi list,
>
> can I mount a device mounted as lustre a second time as ldiskfs or would MMP protect me from doing this?
>
>
> Regards, Michael
>
> _______________________________________________
> Lustre-devel mailing list
> Lustre-devel at lists.lustre.org
> http://lists.lustre.org/mailman/listinfo/lustre-devel
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Lustre-devel] mounting a device twice
2013-07-25 2:39 ` Dilger, Andreas
@ 2013-07-25 5:13 ` Michael Kluge
0 siblings, 0 replies; 3+ messages in thread
From: Michael Kluge @ 2013-07-25 5:13 UTC (permalink / raw)
To: lustre-devel
Hi Andreas,
thanks for the information.
Michael
On 25.07.2013 04:39, Dilger, Andreas wrote:
> You can do this because the kernel is not actually mounting the block device twice. Lustre is mounting the block device internally as type ldiskfs and the second mount will be like a bind mount of the same filesystem root tree.
>
> I do this on my local filesystem for quick debugging, but it isn't strictly safe on an active filesystem because modifications can render the Lustre and on disk state inconsistent.
>
> Cheers, Andreas
>
> On 2013-07-24, at 11:27, "Michael Kluge" <michael.kluge@tu-dresden.de> wrote:
>
>> Hi list,
>>
>> can I mount a device mounted as lustre a second time as ldiskfs or would MMP protect me from doing this?
>>
>>
>> Regards, Michael
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2013-07-24 17:26 [Lustre-devel] mounting a device twice Michael Kluge
2013-07-25 2:39 ` Dilger, Andreas
2013-07-25 5:13 ` Michael Kluge
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