Diomidis Spinellis wrote: > Diomidis Spinellis wrote in freebsd-stable_at_: >> I can't get an Ultrium-2 LTO drive to stream, and (I think) I've >> traced the problem to the read performance of the USB2-attached NTFS [...] >> I'd appreciate any suggestions you may have. > > Today I upgraded the machine to 8.0-CURRENT, and obtained similar results: > - 5372041 bytes/sec reading an NTFS file > - 15369758 bytes/sec reading from the raw device > > The raw/FS read performance difference with UFS is a lot lower: > - 33162654 bytes/sec reading a UFS file > - 47221133 bytes/sec reading from the raw device > > I'd welcome any ideas on why the NTFS layer makes reading three time > slower than reading from the raw device and suggestions for improving > the performance. I'd also be happy to work on improving the situation, > if I get any pointers on where to start. [Apologies for talking to myself.] It looks like the problem is the small (4K) block size NTFS uses for its requests. iostat -t da -zx -w 1 NTFS file: device r/s w/s kr/s kw/s wait svc_t %b da0 1329.6 0.0 5318.5 0.0 1 0.7 95 Raw device: device r/s w/s kr/s kw/s wait svc_t %b da0 234.8 0.0 15024.4 0.0 1 6.3 100 iostat -z -w1 NTFS file: tty ad0 da0 cpu tin tout KB/t tps MB/s KB/t tps MB/s us ni sy in id 0 77 0.00 0 0.00 4.00 1324 5.17 0 0 1 0 99 0 78 0.00 0 0.00 4.00 1331 5.20 0 0 1 0 99 0 78 0.00 0 0.00 4.00 1322 5.16 0 0 0 0 100 0 79 0.00 0 0.00 4.00 1331 5.20 0 0 0 0 100 Raw device: tty ad0 da0 cpu tin tout KB/t tps MB/s KB/t tps MB/s us ni sy in id 0 228 8.00 1 0.01 64.00 236 14.73 0 0 0 0 100 0 78 0.00 0 0.00 64.00 235 14.67 0 0 0 0 100 0 78 0.00 0 0.00 64.00 235 14.67 0 0 0 0 100 0 78 0.00 0 0.00 64.00 235 14.67 0 0 0 0 100 Diomidis Spinellis - http://www.spinellis.grReceived on Wed Jan 23 2008 - 21:31:04 UTC
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