dd(1) performance when copiing a disk to another

[Steven Hartland]

That's actually pretty good for a sustained read / write on a single disk.

    Steve
----- Original Message ----- 
From: "Patrick Proniewski" <patpro at patpro.net>
To: <freebsd-performance at freebsd.org>
Sent: Sunday, October 02, 2005 3:57 PM
Subject: dd(1) performance when copiing a disk to another


Hi,
(carte mère supermicro
chip SATA Intel 6300ESB)

I run FreeBSD 5.4 on a PIV 3GHz (SuperMicro motherboard, Intel SATA
6300ESB chipset) with 2 SATA HDD. I'm in the process to duplicate the
boot HDD to the second HDD. I run dd for that:

# dd if=/dev/ad4 of=/dev/ad6 bs=1m

It yields to poor performances:

$ iostat -dhKw 1
(...)
              ad4              ad6
   KB/t tps  MB/s   KB/t tps  MB/s
  124.49 252 30.69  128.00 246 30.69
  128.00 285 35.64  128.00 279 34.90
  128.00 282 35.27  128.00 283 35.40
(...)

Is it normal that data rate won't go upper than 35/38 MB/s ?

HDDs are: ad4 -> Maxtor 80 Go 7200 rpm
           ad6 -> Hitachi 80 Go 7200 rpm

one more question: is dd(1) a good way to duplicate a boot drive to
make a bootable spare disk ?

patpro_______________________________________________
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