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OpenBSD General Other questions regarding OpenBSD which do not fit in any of the categories below. |
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Disk I/O Throughput
I've an question regarding disk I/O throughput.
The observation: When I cp a 1 GB file within sd0 it takes about 100 sec. When I attach sd1 via USB2 and cp the file from sd0 it takes about 80 sec. When I cp this file back from sd1 to sd0 it takes about 40 sec. The disk specs: sd0 at scsibus0 targ 0 lun 0: <ATA, Hitachi HTS54161, SB4O> SCSI3 0/direct fixed sd0: 152627MB, 19457 cyl, 255 head, 63 sec, 512 bytes/sec, 312581808 sec total sd1 at scsibus1 targ 1 lun 0: <SAMSUNG, HD401LJ, 0-15> SCSI2 0/direct fixed sd1: 381554MB, 48641 cyl, 255 head, 63 sec, 512 bytes/sec, 781422768 sec total Now I wonder why it takes longer to cp a file within sd0 than from/to sd1. I also would like to know if my disk throughput performs averagely. tak sa mycket! Edit: P.S. And when I cp the file within sd1 it takes about 120 sec. Last edited by m4rc; 9th July 2008 at 04:33 PM. |
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I suspect you are witnessing the effects of buffering. A portion of the file may still exist in the hard drive's buffer, so the amount of time needed to copy to an external device is smaller.
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So the read/write capability of my drives vary between 8 and 25 MB/sec. incl. "buffer effects". According to the USB 2.0 (60 MB/sec.) and SATA 300 (300 MB/sec.) specs it looks that there is still some potential left to improve the read/write speed of my disks. Or do I simply confuse read/write capability with bus bandwidth?
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Hello,
Quote:
__________________
And the WORD was made flesh, and dwelt among us. (John 1:14) |
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Thanks for debugging me ;-)
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