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Hi, This is slightly off-topic, but nontheless important for the setup of large direct attached storage systems typically used with xrootd. Maybe some of you have good suggestions or experiences. For our next upgrade of our Tier2 I would need a benchmark with which I can measure whether I can satisfy an I/O requirement per worker node (WN, or CPU core). This has to be tested while all WNs are reading in parallel from all file servers. I just want to assume that the clients from the WNs are reading in a nicely distributed fashion from the file servers, e.g. in the case of 10 file servers and 150 WNs, I would assume that in average 15 WNs are reading at the same time from any file server. But any combination of 15 WNs must be able to yield the desired bandwidth. Naturally, this benchmark is targeted at mimicking a cluster running analysis applications. A primitive test (but not exactly matching the use case) could be using netperf or iperf in UDP mode. E.g. the file servers would receive packets from the required fraction of worker nodes (The sending intervals and packet sizes can be set for netperf). One would gradually increase the sending rate per worker node until UDP packet loss is observed. I'm glad for any suggestions. Cheers, Derek -- Dr. Derek Feichtinger Tel: +41 56 310 47 33 AIT Group email: [log in to unmask] PSI http://people.web.psi.ch/feichtinger CH-5232 Villigen PSI