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
>
