Date: Wed, 5 Oct 2005 19:30:24 +0200 From: Patrick Proniewski <patpro@patpro.net> To: freebsd-performance@freebsd.org Subject: Re: dd(1) performance when copiing a disk to another Message-ID: <3509E78F-E90F-4056-AD4C-FDDDC41A4A46@patpro.net> In-Reply-To: <E6243148329F3A468BC8F98468FC4BB404616855@fw1-ex03.c-b.net> References: <E6243148329F3A468BC8F98468FC4BB404616855@fw1-ex03.c-b.net>
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Hi, thank you all for these interesting explanations. I've made some more tests with my disks : As you'll see, for block size greater than 64k, the HDD ad6 (hitachi) is the bottleneck. bs of 1m and 512k yield to best transfert rates between ad4 and ad6 and using a pipe between to dd will lower the performance. best regards, and thank you again, Pat, #### /dev/zero to ad6 # dd if=/dev/zero of=/dev/ad6 bs=1m count=1000 1000+0 records in 1000+0 records out 1048576000 bytes transferred in 31.047655 secs (33773114 bytes/sec) # dd if=/dev/zero of=/dev/ad6 bs=8k count=128000 128000+0 records in 128000+0 records out 1048576000 bytes transferred in 31.580223 secs (33203565 bytes/sec) #### ad4 (SATA150) to ad6 (SATA150) # dd if=/dev/ad4 of=/dev/ad6 bs=8k count=128000 128000+0 records in 128000+0 records out 1048576000 bytes transferred in 50.916216 secs (20594146 bytes/sec) # dd if=/dev/ad4 of=/dev/ad6 bs=64k count=16000 16000+0 records in 16000+0 records out 1048576000 bytes transferred in 30.925397 secs (33906630 bytes/sec) # dd if=/dev/ad4 of=/dev/ad6 bs=128k count=8000 8000+0 records in 8000+0 records out 1048576000 bytes transferred in 31.462153 secs (33328170 bytes/sec) # dd if=/dev/ad4 of=/dev/ad6 bs=256k count=4000 4000+0 records in 4000+0 records out 1048576000 bytes transferred in 30.819234 secs (34023428 bytes/sec) # dd if=/dev/ad4 of=/dev/ad6 bs=512k count=2000 2000+0 records in 2000+0 records out 1048576000 bytes transferred in 30.589651 secs (34278783 bytes/sec) # dd if=/dev/ad4 of=/dev/ad6 bs=1m count=1000 1000+0 records in 1000+0 records out 1048576000 bytes transferred in 30.660553 secs (34199514 bytes/sec) # dd if=/dev/ad4 bs=1m count=1000 | dd of=/dev/ad6 bs=1m 1000+0 records in 1000+0 records out 1048576000 bytes transferred in 33.998716 secs (30841635 bytes/sec) 0+16000 records in 0+16000 records out 1048576000 bytes transferred in 34.001099 secs (30839474 bytes/sec)
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