Thanks for this - sorry for sounding grouchy earlier, but it has been a
particularly frustrating day...
John
On 03/08/2012 15:25, Sam Skipsey wrote:
> Okay:
>
> So, dpns-ls lists the entries in the DPNS namespace.
> This is not the same as the physical file namespace (and indeed,
> shouldn't be - since replicas work by having multiple physical files
> behind a single DPNS filename).
>
> dpm-list-disk lists all of the physical filenames known about by DPM
> for a given disk (and filesystem).
>
> dpm-disk-to-dpns does that, and also gives you the locations in the
> DPNS namespace for all of those files.
>
> dpm-delreplica lets you delete a specific replica (that is: a
> particular physical file path, not a DPNS entry) from DPM.
>
> You probably want to use dpm-delreplica if you know that there are
> multiple replicas of a file.
> (If you don't then you probably want to try rfrm, to use the
> lower-level rfio interface to remove the file, or dpns-rm (optionally
> with the -f force option) to remove the DPNS entry for the file -
> which means that DPM will no longer know about it.)
>
> Sam
>
>
> On 3 August 2012 15:16, John Hill <[log in to unmask]> wrote:
>> On 03/08/2012 13:49, Sam Skipsey wrote:
>>>
>>> On 3 August 2012 13:38, Ewan MacMahon <[log in to unmask]>
>>> wrote:
>>>>>
>>>>> -----Original Message-----
>>>>> From: Testbed Support for GridPP member institutes [mailto:TB-
>>>>> [log in to unmask]] On Behalf Of John Hill
>>>>>
>>>>> I thought dpns-rm was the right tool, but when I tried it on one of
>>>>> the files I'm trying to remove I got a "File Exists" message, which
>>>>> confused me sufficiently to make me think that it wasn't trying to do
>>>>> the
>>>>> correct thing. At least I now know I'm on the right track.
>>>>>
>>>> I think we usually wind up using rfrm for this, so the basic
>>>> sequence of events is to use dpm-disk-to-dpns to get a list of
>>>> everything that used to be on the dead filesystem, then split
>>>> the lines in that output to give you just a list of the DPNS
>>>> names (it gives you the filesystem paths as well), then rfrm
>>>> the files by DPNS name. I have a vague recollection of doing
>>>> something properly handle files that have multiple replicas,
>>>> but I've just been looking for the details of that and haven't
>>>> found it yet.
>>>>
>>>
>>> I'm fairly sure I did write something to do this.
>>> (For multiple replicas, dpns-delreplica should work, if you know which
>>> replica you want to remove, as it was written for this by Greig.)
>>>
>>> Sam
>>>
>>>> Ewan
>>
>>
>> The background to this is that I need to remove the DPNS entries for my
>> failed diskserver - I think that just means deleting the particular replica
>> which is lost. I would have thought that dpns-ls was the right tool, but
>> then I'm finding that understanding how to do things in GRID Management
>> makes reading the Rosetta Stone look like light relaxation.
>>
>> John
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