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“L1/L2 farm: some thought ”

“L1/L2 farm: some thought ”. G.Lamanna , R.Fantechi & D. Di Filippo (CERN) Computing WG – 28.9.2011. The “Old” online farm. L1 farm. L2 farm. L1 = M pc, L2 = N pc Blue Switch  (M+40+1) ports mono- directionals Green switch  (N+M+40+1) ports bi- directionals. < 5 0 Gb /s.

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“L1/L2 farm: some thought ”

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  1. “L1/L2 farm: some thought” G.Lamanna, R.Fantechi & D. Di Filippo (CERN) ComputingWG – 28.9.2011

  2. The “Old” online farm L1 farm L2 farm • L1 = M pc, L2 = N pc • Blue Switch  (M+40+1) ports mono-directionals • Green switch  (N+M+40+1) ports bi-directionals <50 Gb/s 40x10 Gb/s 40x10 Gb/s 180 Gb/s 2.5 Gb/s CDR 1 x10 Gb/s CREAM Services (DCS, Boot, …)

  3. The “new” online farm L1/2 farm TCP or UDP? • Blue switch  (N+M+40+40+1+1+1) bidirectionals ports • Number of ports available for computing = Ntot(128) – 83 = 35 <50 Gb/s 40x10 Gb/s 40x10 Gb/s 180 Gb/s 2.5 Gb/s Storage farm CDR CREAM 1 x10 Gb/s Services (DCS, Boot, …)

  4. Advantages: more efficient reuse of PCs, smaller number of PCs • Disavantages: bottleneck, transmission protocol, switch cost and support , flexibility and limited upgradability (up to the switch back plane capability)

  5. <50 Gb/s • Blue switch as before • Each PC elaborates one single event (both L1 and L2) instead of a fraction of event • No needed of routing among the PCs (no problem on protocol, no latency due to the network, …) 40x10 Gb/s 40x10 Gb/s Only final results L1/2 farm 180 Gb/s 2.5 Gb/s CREAM CDR 1 x10 Gb/s 2.5 Gb/s Storage farm Services (DCS, Boot, …)

  6. ev: #123 L1 – CHOD L1 – RICH L1 – MUV L1 – MUV … LKr DATA Merging L2 ev: #123 L1 – RICH (fragment) Switch Switch ev: #124 L1 – CHOD L1 – RICH L1 – MUV L1 – MUV … LKr DATA Merging L2 • From the PCs to the switch = L1 trigger request for the LKr (peanuts) and final events for CDR (2.5 Gb/s) • Max rate per PC: 180 Gb/s / (Number of PC) • Multiprocessor PCs: the parallelism is exploited at the PC levels instead of at network level. • Routing strategies at TEL62 level similar to the Jonas farm (the round robin with “per burst routing table upgrade” is a little bit more safe) ev: #123 L1 – CHOD (fragment) ev: #125 L1 – CHOD L1 – RICH L1 – MUV L1 – MUV … LKr DATA Merging L2 ev: #123 L1 – MUV (fragment) ev: #126 L1 – CHOD L1 – RICH L1 – MUV L1 – MUV … LKr DATA Merging L2 ev: #123 L2 - merge (Full event)

  7. Switch • Since the routing is univocal/injective (the PC doesn’t to talk each other) a tree structure can be foreseen: upgradability and smaller switches (cost) • Still open the possibility to use 1 Gb instead of 10 Gb

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