Re: Fast Disk Writes

[cary@agora.rdrop.com (David Cary)]

>From: Felix Gorokhovsky <fg60@columbia.edu>
...
>I get the same results writing to a Jaz or SCSI hard drive( both are on
>the same scsi bus in my computer). I tried different sizes of buffers from
>one byte to 100 000 bytes. I could never get more than 1.1 Mb/s while
>writing 900 GB file.

Wierd. Well, there's obviously a bottleneck somewhere. Perhaps you have a
inefficient SCSI device driver, or a poorly engineered SCSI interface, or a
bug in your C compiler, or ...

Does your program work OK on your boot disk (I assume IDE HD) ?

Tangential note: I read "1 Mb/s" a "One Mega-bit per second", while "1
MB/s" becomes "One Mega-Byte per second". (Capital units are always bigger
than lowercase units; 1 Mm is much bigger than 1 mm). I have a slight
preference for "b" (bits), since it *is* the fundamental unit of
information. I haven't seen a new "B" Byte-oriented interface in a long
time -- they're either serial or swinging to the other extreme of 32 or 64
bits (soon even more!) at a time.

>From: John R Pierce <pierce@hogranch.com>
...
David wrote:
>>Try writing to a (SCSI) fixed-disk drive and see if it goes
>>any faster.
>
>you mailed this to the wrong dude!  I was also replying to the original...

Whoops. Sometimes it is difficult for me to figure out who wrote what on
these mailing list thangs.

>SCSI jaz drives are actually fairly quick.
...
>Actually, the ISA bus itself can sustain xfers around 6 to 8MByte/sec [2
>clocks at 8MHz per 16bits].
...
>-jrp

Thanks for the info. I thought it was interesting. Learned something I
didn't know.

David Cary "mailto:d.cary@ieee.org" "http://www.rdrop.com/~cary"
Future Tech, quantum computing, digital hologram, PCMCIA, <*> O-

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