Søren Schmidt wrote: >> # dd if=/dev/ad4 of=/dev/null bs=1024k count=1024 >> 1024+0 records in >> 1024+0 records out >> 1073741824 bytes transferred in 31.090536 secs (34535970 bytes/sec) > > etc, and I get this: > 1073741824 bytes transferred in 18.488903 secs (58074934 bytes/sec) > 1073741824 bytes transferred in 14.956484 secs (71791059 bytes/sec) >> I'd like to know wich is you opinion about this. > > If you run a stock generic kernel with the debug (WITNESS etc) taken out > you should see the same raw performance as I do. I redid all tests with __RC1__ and performance is as bad as before. > Now, raw performance is one thing, filesystem I/O something entirely I think the problem is with raw performace, just see this example with a test raid0. Each disk by separate has a throughput of 26000 K/sec, with /dev/stripe/test they have a throughput of 15000 K/sec each (raid0 throughput 30000 K/sec) and with four disks 7500 K/sec each (30000 K/sec again). # dd if=/dev/stripe/test of=/dev/null bs=1024k count=1024 1024+0 records in 1024+0 records out 1073741824 bytes transferred in 30.072215 secs (35705445 bytes/sec) There is a constant limit of 30000 K/sec independent of the number of disks used. simply it doesn't makes any sense. With two disk I'd must have approx. 26K+26K=52 M/sec and with four 26K+26K+26K+26K=104 M/sec Other systems like OpenBSD had a good throughput 55000K/sec by disk I send you in another email with all info that you need. Regards,Received on Tue Oct 19 2004 - 09:39:58 UTC
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