SBND dCache storage » History » Version 1

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Gianluca Petrillo, 09/26/2016 01:52 PM

SBND dCache storage

dCache area consists of a huge data space, made of tapes and disks.
SBND owns one of each of two types of dCache areas. Each of them has room for areas owned by a single user:

  • scratch (/pnfs/sbnd/scratch/users/${USER}): files in this area can be deleted automatically; you can store a grid job result there waiting to transfer it into a safe place, but don't rely on leaving your important stuff there for long
  • persistent (/pnfs/sbnd/persistent/users/${USER}): files in this area will not be deleted

We have a limited quota of space as well, so fill it responsibly.

Remote access to dCache areas

While dCache areas may happen to be available on some local nodes (e.g., SBND GPVM's), in general the area is not directly reachable.
We use a tool called IFDH to fetch files from wherever they are. Also some code uses IFDH to fetch files: among them, LArSoft modules CORSIKAGen and GENIEGen.

IFDH sometimes requires the user to be authenticated, which is usually achieved by a certificate.
The ritual for getting the required authorisations goes like this:

kinit "${USER}@FNAL.GOV"                                                     # get your Kerberos authentication
kx509                                                                        # ask Kerberos for a x509 certificate
voms-proxy-init -noregen -rfc -voms 'fermilab:/fermilab/sbnd/Role=Analysis'  # create a "proxy" from the certificate

The last line of the output from this sequence should look something like:
Your proxy is valid until Tue Sep 27 01:49:24 2016

where the date is 24 hours in the future. This "proxy" is what we need to get our job done.

This is the same procedure as for getting credentials to submit jobs.