Re: [eug-lug]Dexter's dd block size speed test
On Fri, Aug 15, 2003 at 09:26:44AM +0100, Jamie Kitson wrote: > Hi, I got your address after reading about your dd bs speed test. Me and a > friend are having an argument, he recons that your test is tainted by your > hardware... can you prove him wrong for me? > > Thanks, Jamie Jamie, that test was probably in a very old email. Please repost the relevant portions. Anyway, the test is testing hardware, so of course it is "tainted" or "biased" or dependent upon the very hardware it is testing. Cory -- Cory Petkovsek Adapting Information Adaptable IT ConsultingTechnology to your (541) 914-8417 business [EMAIL PROTECTED] www.AdaptableIT.com ___ EuG-LUG mailing list [EMAIL PROTECTED] http://mailman.efn.org/cgi-bin/listinfo/eug-lug
[eug-lug]Dexter's dd block size speed test
Hi, I got your address after reading about your dd bs speed test. Me and a friend are having an argument, he recons that your test is tainted by your hardware... can you prove him wrong for me? Thanks, Jamie ___ EuG-LUG mailing list [EMAIL PROTECTED] http://mailman.efn.org/cgi-bin/listinfo/eug-lug
Re: [Eug-lug]Dexter's dd block size speed test
Dex, nice research ! (-: A few comments: some details of what you found (and others commented on) may depend on the intelligence built into the on-board disk controller (re-mapping bad sectors, buffering I/O, ...) - The default bs=512 matches a 'sector' (floppy disk, MBR) and also should remain for backward compatibility of older custom scripts (or custom scripts *should be* specific regarding defaults, (hmm, myself ...). - in case you are considering writing to the author of 'dd', please add this on my behalf: The reported transferred data should not just be 'n+1 records in/out' but 'n blocks + xyz bytes in/out' -- the prog knows 'xyx' (so that's easy to implement), and such output would provide the user with exact information w/o further doubts) - Horst On Sat, 14 Dec 2002, Dexter Graphic wrote: > Purpose: > I wanted to find out what effect changing the block size (bs=) > option of the dd command would have on partition copy speeds. > I also wanted to confirm that the default block size (if no bs > option was specified) was indeed 512 bytes as someone had said. > > Procedure: > 1.) I used dd to completely fill up a 75MB partition with data > from a larger partition. > > /dev/hda1 = Debian 3.0 root, ext3 > /dev/hda3 = an empty, unformatted partition > command used = "dd if=/dev/hda1 of=/dev/hda3" > (Note: the above command stops copying and aborts once it has > used up all the available space on /dev/hda3.) > > 2.) I then copied this 75MB partition to an identical partition > on an identical drive using various block sizes and timing the > process. > > time dd if=/dev/hda3 of=/dev/hdb3 bs=xx > > Results: > > no bs= 78s 144584+0 records > bs=512 78s 144584+0 records > bs=1k 38s 72292+0 records > bs=2k 38s 36146+0 records > bs=4k 38s 18073+0 records > bs=5k 39s 14458+1 records > bs=50k 38s 1445+1 records > bs=500k 39s 144+1 records > bs=512k 39s 144+1 records > bs=1M 39s 72+1 records > bs=5M 39s 14+1 records > bs=10M 39s 7+1 records > > Conclusions: > > 1. The default block size if no bs= option is specified is > 512 bytes. > > 2. Any block size larger than the default (512 bytes) will > double the copy speed, but using larger block sizes will not > result in proportionately greater speed increases. > > 3. The output of dd shows the number of blocks (records) copied > plus (+) the number of partial blocks copied. From the above > results I recalled that my hda1 partition was initialized using > a 4k block size (which was the default block size in cfdisk). > > 4. The dd man page should be updated to include this basic > operational information (conclusions 1 thru 3) so that people > don't have to run their own tests to figure out how to use it. > > 5. The dd code should *probably* be updated so that 4k is the > default block size rather than 512 bytes (since this seems to > be the default block size on modern hard disks and it results > in doubling of the copy speed. > > Dexter Graphic > > ___ > Eug-LUG mailing list > [EMAIL PROTECTED] > http://mailman.efn.org/cgi-bin/listinfo/eug-lug > ___ Eug-LUG mailing list [EMAIL PROTECTED] http://mailman.efn.org/cgi-bin/listinfo/eug-lug
[Eug-lug]Dexter's dd block size speed test
Purpose: I wanted to find out what effect changing the block size (bs=) option of the dd command would have on partition copy speeds. I also wanted to confirm that the default block size (if no bs option was specified) was indeed 512 bytes as someone had said. Procedure: 1.) I used dd to completely fill up a 75MB partition with data from a larger partition. /dev/hda1 = Debian 3.0 root, ext3 /dev/hda3 = an empty, unformatted partition command used = "dd if=/dev/hda1 of=/dev/hda3" (Note: the above command stops copying and aborts once it has used up all the available space on /dev/hda3.) 2.) I then copied this 75MB partition to an identical partition on an identical drive using various block sizes and timing the process. time dd if=/dev/hda3 of=/dev/hdb3 bs=xx Results: no bs=78s 144584+0 records bs=51278s 144584+0 records bs=1k 38s 72292+0 records bs=2k 38s 36146+0 records bs=4k 38s 18073+0 records bs=5k 39s 14458+1 records bs=50k38s 1445+1 records bs=500k 39s 144+1 records bs=512k 39s 144+1 records bs=1M 39s 72+1 records bs=5M 39s 14+1 records bs=10M39s 7+1 records Conclusions: 1. The default block size if no bs= option is specified is 512 bytes. 2. Any block size larger than the default (512 bytes) will double the copy speed, but using larger block sizes will not result in proportionately greater speed increases. 3. The output of dd shows the number of blocks (records) copied plus (+) the number of partial blocks copied. From the above results I recalled that my hda1 partition was initialized using a 4k block size (which was the default block size in cfdisk). 4. The dd man page should be updated to include this basic operational information (conclusions 1 thru 3) so that people don't have to run their own tests to figure out how to use it. 5. The dd code should *probably* be updated so that 4k is the default block size rather than 512 bytes (since this seems to be the default block size on modern hard disks and it results in doubling of the copy speed. Dexter Graphic ___ Eug-LUG mailing list [EMAIL PROTECTED] http://mailman.efn.org/cgi-bin/listinfo/eug-lug
