URL:
<http://savannah.cern.ch/support/?135998>
Summary: How to let cmsd export a subset of the files
Project: XROOTD
Submitted by: boccali
Submitted on: 2013-02-19 08:59
Category: None
Priority: 5 - Normal
Severity: 3 - Normal
Status: None
Privacy: Public
Assigned to: None
Originator Email:
Open/Closed: Open
Discussion Lock: Any
Operating System: GNU/Linux
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Details:
Ciao,
in the journey (up to now successful - thanks to this list) to enable a CMS
Storm based Tier1 to Xrootd, I have an additional question.
At CNAF, we have GPFS as FS, with a tape backend using TSM.
For safety / performance reasons, we would not like Xrootd to trigger tape
recalls. Hence, we would like Xrootd CMSD to respond to locate queries from
the upper level redirector not just by checking if a file exists (GPFS+TSM
show via "stat" all files in the filesystem), but also if the file is on the
disk buffer.
So, we would need a hook on top of 'stat', which does basically a
'getfattr':
for a pinned file:
# file: B02A0EC4-340D-E211-BD28-00237DDC5BBC.root
user.storm.checksum.adler32="80c4e0b9"
user.storm.migrated
user.storm.pinned="1350151948"
for a file only on tape:
# file: F0A20102-5378-E211-BA76-20CF3027A5F3.root
user.storm.checksum.adler32="76033838"
user.storm.migrated
so we can parse the output to know where it is pinned or not ...
We would need a place (an hook? a specific API?) where to plug in this
additional check upon a request for the availability of a file ..
cheers
tommaso
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