Hi,
A follow question concerning how the config file would be handled by
systems with one mount.
Consider:
oss.cache public /xrd/cache*
xrootd.fslib /opt/xrootd/lib/libXrdOfs.so
xrootd.export /xrd
On systems with multiple partitions, I would mount:
/xrd
/xrd/cache00
...
/xrd/cacheNN
On systems with one partition, I would mount /xrd
Will this work, or does the oss.cache directive need to wrapped in a
conditional statement so that it is only used on multi-partition servers?
Patrick
Wilko Kroeger wrote:
>
> Hello Patrick
>
> Fabrizio answered already most of the question. I just have a few comments.
>
> If you have more then one partition that an xrootd server should serve
> you should use the cache directive.
> The cache is working by placing a file in a cache directory and creating
> a link between this file and the proper file name. For example:
> if the file name is /xrd/test/d1/file1 and your you use the the cache
> directive
> ooss.cache /xrd*
> the file would be put (lets pick cache xrd2) into
> /xrd2/%xrd%test%d1%file1
> and a link is created:
>> ls -l /xrd/test/d1/file1 -> /xrd2/%xrd%test%d1%file1
>
> As you can see there are no directories in the cache. The file name in
> the cache is the proper file name with all '/' replaced by '%'.
>
>
> As xrootd will export /xrd you have to create a /xrd directory. I guess
> this will not be in the '/' root partition but in one of you data
> partition (/xrd1 /xrd2) and therefore you will need a link.
> /xrd -> /xrd1
>
> However, in this case, doing an 'ls /xrd' would list all files in /xrd1
> which could be quite large depending how many files you have. Therefore,
> you might want to have a link like
> /xrd -> /xrd1/xrd
> In this case 'ls /xrd' would not list the files in the /xrd1 cache.
>
> Another possibility would be to make the cache directories a little bit
> more explicit. Mount your two partitions as:
> /xrd
> /xrd/cache1
> and create the directory
> /xrd/cache0
> and then use
> ooss.cache /xrd/cache*
>
> I hope these comments helped a little bit.
>
> Cheers,
> Wilko
>
>
>
> On Wed, 7 Nov 2007, Patrick McGuigan wrote:
>
>> Hi,
>>
>> I am setting up an xrootd cluster for the first time and I have a
>> question about the oss.cache directive.
>>
>> Some of my data servers have two partitions (and some have one) that I
>> want to use for storage. Is it true that the oss.cache directive MUST
>> be used to put two partitions into service? How is load balancing
>> (based on space) managed on caches versus partitions? Are there any
>> performance penalties to using the cache directive?
>>
>> Finally, when a directory is created within a cache, does the
>> directory get created on both partitions?
>>
>>
>>
>> If the partition on a one mount server is /xrd1 and the partitions on
>> dual-mount server are /xrd1 and /xrd2, would the following snippet
>> from the config file be appropriate:
>>
>>
>> #
>> #
>> olb.path rw /xrd
>> #
>> oss.cache public /xrd*
>> #
>> xrootd.fslib /opt/xrootd/lib/libXrdOfs.so
>> xrootd.export /xrd
>>
>>
>>
>> I am expecting this to create a global namespace rooted at /xrd that
>> is writable and would use both partitions of dual-mount data server.
>>
>>
>>
>> Thanks for any information,
>>
>> Patrick
>>
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