Matthew Dillon scribbled this message on Nov 7:
> When you write to a raw disk with your dd, it is reading a block from
> /dev/zero into its local buffer which involves a zeroing operation
> that the read code never had to do, then dd writes the buffer to disk.
thank you! this is exa
:well, I am working on writing a capture program to do 640x480x12bpp@30fps
:to a raw disk, but writing to the raw device is SOOO slow... the reason
:I say it's slow is the fact that it takes 8 times the system time writing
:than reading...
:
:a bit about the system... k6/2-250, 100mhz system bus
Jonathan Lemon scribbled this message on Nov 6:
> Try doing `iostat 1' while doing the transfers. This is what I see here:
>
> tty da0 da1 da2 cpu
> tin tout KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s us ni sy in id
> TEST A:0.
In article [EMAIL PROTECTED]> you
write:
>well, I am working on writing a capture program to do 640x480x12bpp@30fps
>to a raw disk, but writing to the raw device is SOOO slow... the reason
>I say it's slow is the fact that it takes 8 times the system time writing
>than reading...
>
>a bit about
John-Mark, have you double checked your numbers? I get:
rsnow@basil% time dd if=/dev/vinum/rstripe of=/dev/null bs=64k
count=2048
2048+0 records in
2048+0 records out
134217728 bytes transferred in 8.096565 secs (16577120 bytes/sec)
0.016u 0.482s 0:08.09 6.0% 73+370k 0+0io 0pf+0w
On vinum
{ Moved to FreeBSD-Questions }
Emm, I want your system. Have you double checked your numbers? They
look a bit high. Here's what I get on a vinum stripe across two 'cudas
on an SMP box:
rsnow@basil% time dd if=/dev/vinum/rstripe of=/dev/null bs=64k
count=2048
2048+0 records in
2048+0 records ou
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