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Ah, another thing. I committed an experimental but working (I hope!) version of the new xfer/caching algorithm. It would be very very nice to have some feedback about its performance, since one of its sub-products (together with the concurrent xfers) is that the requests are almost sorted. I wonder if this would increase or decrease the performance in your case. BTW: what is your case? Histograms from ROOT files? Reconstruction? Analysis? Fabrizio Fabrizio Furano wrote: > Hi Derek, > > Derek Feichtinger wrote: >> 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. >> > > Well, I don't know exactly your requirements, but wouldn't it be > sufficient to look at the traffic by making an average of the data seen > by each client after the file close ? > > Another (better) way could be to setup XrdMon. Why not ? > > > Fabrizio > > >> 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 >>