Monday, 5 July 2010

LHCb token full: game over, insert coin?

This is what happened las 23rd June. The MC-M-DST space token of the LHCb experiment at PIC got full and, according to the monitoring, we are stuck since then.
PIC is probably the smallest LHCb Tier1. Smallest than the average, and this probably creates some issues for the LHCb data distribution model. At first order, they consider all Tier1 the same size so essentially all DST data should go everywhere.
PIC can not pledge 16% of the LHCb needs for various reasons, so this is why some months ago we agreed with the experiment that, in order to still make an efficient use of the space we could provide, the data stored should be somehow "managed". In particular, we agreed that we could just keep the "two last versions" of the reprocessed data at PIC instead of keeping a longer history. Looked like a fair compromise.
Now we have our token full and looks we are stuck. It is time to check if that nice idea of "keeping only the two most recent versions" can actually be implemented.

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