On 21 Jul 2011 at 20:15, yudi v wrote: Date sent: Thu, 21 Jul 2011 20:15:39 +1000 Subject: Re: Overwriting a 4096 byte sector harddisk drive with random data From: yudi v <yudi.tux@xxxxxxxxx> To: Community support for Fedora users <users@xxxxxxxxxxxxxxxxxxxxxxx> Send reply to: Community support for Fedora users <users@xxxxxxxxxxxxxxxxxxxxxxx> <mailto:users-request@xxxxxxxxxxxxxxxxxxxxxxx?subject=unsubscribe> <mailto:users-request@xxxxxxxxxxxxxxxxxxxxxxx?subject=subscribe> > > > > On Thu, Jul 21, 2011 at 8:04 PM, Gilboa Davara <gilboad@xxxxxxxxx> wrote: > On Thu, 2011-07-21 at 19:48 +1000, yudi v wrote: > > Hi > > From what I understand, the first command above will write data in > > 512 byte blocks, the second one in 1MB blocks, and the third in > 4096 > > byte blocks. Right? > > Yep. > The 1M should also yield considerably better performance. > (Though the > random number generator may cap the performance in this > case). > > - Gilboa > > - > > Sorry, could you please elaborate a bit more on how a higher size block results in better > performance. I maintain a disk imaging project, and bs can make a big difference depending on the disk and hardware being used. Here is a quick set of test I just did creating a 10MB file from urandom on my system. You may get higher or lower results depending on your hardware and the size of the file or disk. time dd if=/dev/urandom of=test1 bs=1M count=10 10+0 records in 10+0 records out 10485760 bytes (10 MB) copied, 1.23827 s, 8.5 MB/s real 0m1.241s user 0m0.000s sys 0m1.222s time dd if=/dev/urandom of=test1 bs=4096 count=2560 2560+0 records in 2560+0 records out 10485760 bytes (10 MB) copied, 1.26018 s, 8.3 MB/s real 0m1.264s user 0m0.001s sys 0m1.241s time dd if=/dev/urandom of=test1 bs=512 count=20480 20480+0 records in 20480+0 records out 10485760 bytes (10 MB) copied, 1.3672 s, 7.7 MB/s real 0m1.371s user 0m0.002s sys 0m1.352s > > -- > Kind regards, > Yudi > +----------------------------------------------------------+ Michael D. Setzer II - Computer Science Instructor Guam Community College Computer Center mailto:mikes@xxxxxxxxxxxxxxxx mailto:msetzerii@xxxxxxxxx http://www.guam.net/home/mikes Guam - Where America's Day Begins G4L Disk Imaging Project maintainer http://sourceforge.net/projects/g4l/ +----------------------------------------------------------+ http://setiathome.berkeley.edu (Original) Number of Seti Units Returned: 19,471 Processing time: 32 years, 290 days, 12 hours, 58 minutes (Total Hours: 287,489) BOINC@HOME CREDITS SETI 11023792.670369 | EINSTEIN 6216520.680851 ROSETTA 3399923.990913 | ABC 6993668.719655 -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
