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Support use of xrootd by HEP experiments

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Subject:
From:
Patrick McGuigan <[log in to unmask]>
Date:
22 Jun 2010 18:59:13 -0500Tue, 22 Jun 2010 18:59:13 -0500
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Thanks Wei,

I had thought that something like this method would be available, does 
your suggestion require a specific configuration in the redirector?  We 
are using the defaults with respect to how the redirector chooses 
dataservers.

Regards,
Patrick

On 06/22/2010 06:54 PM, Yang, Wei wrote:
> Hi Patrick,
>
> If you set all.export path to readonly, you won't be able to delete. I never tried any of this because but here is an idea: You may use cms.space directive to set the minimum space required for the data server to be writeable, and set a high number (above the total space of that data server) so that redirector always think the data server runs out of space. In that case, you can keep on deleting without worrying about new data getting written to it.
>
> regards,
> Wei Yang  |  [log in to unmask]  |  650-926-3338(O)
>
>
> On Jun 22, 2010, at 4:20 PM, Patrick McGuigan wrote:
>
>> Hi,
>>
>>
>> I am preparing to replace 6 smaller dataservers with 2 much larger
>> systems and I am curious if anyone has advice on making the transition.
>>   There is about 40TB of data currently on the smaller dataservers.
>>
>> A couple of caveats:
>> 1) The existing data is organized in cache groups on the dataservers and
>> the cgroup information will need to propagate to the new dataservers
>>
>> 2) The smaller dataservers are in a production system and I want to
>> minimize any downtime associated with data on these servers.
>>
>> 3) A sizable portion of the 40TB is no longer relevant to the production
>> system and potentially could be deleted (or at least not migrated)
>>
>>
>> It eases my burden if I can delete data from all the production
>> dataservers at the same time.  However, if I delete data from the 6
>> servers that will be migrated, I don't want new data to take its place.
>>
>>
>> I was hoping that I could somehow setup the existing dataservers in a
>> readonly configuration but still be able to delete data via the
>> redirector (actually from a FUSE client talking to a CNS service on the
>> redirector).  Is this possible?
>>
>>
>>  From my reading, I can make the dataservers readonly by altering the
>> all.export line:
>>
>> all.export /xrd readonly
>>
>> But I am not sure if this still allows deletions.
>>
>> Also, does the use of oss.cache directives affect the readonly status?
>>
>>
>> If anyone has experience with performing this type of migration, or if
>> anyone has suggestions, I would be very thankful to hear from you.
>>
>> Regards,
>>
>> Patrick
>>
>>
>



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