[tlug] Re: dd block size: Much Faster with Knoppix 5.1.1 CD

[jep200404 <jep200404@example.com>]

Yesterday I wrote: 

> Here's a summary of the time needed to wipe a 20GB drive. 
> 
>    Block Size      Time
>    ----------  -------------
>    1 megabyte   5853 seconds
>    512 bytes   12968 seconds
>    1 byte      60308 seconds (just for fun!) 

That was under Knoppix 4.0.2 CD. 
I had forgotten how slow that version is, 
so I re-ran the commands under Knoppix 5.1.1 CD. [1]

Block Size       Time       Speed
----------  -------------  ---------
1 megabyte    490 seconds  40.8 MB/s
512 bytes    1841 seconds  10.9 MB/s
1 byte      45477 seconds   440 kB/s

This only reinforces the significance of block size on speed. 

Jim

---------------------------------------------------------------

[1]

root@example.com:~# cat /proc/ide/hda/capacity
39102336
root@example.com:~# fdisk -l /dev/hda

Disk /dev/hda: 20.0 GB, 20020396032 bytes
16 heads, 63 sectors/track, 38792 cylinders
Units = cylinders of 1008 * 512 = 516096 bytes

Disk /dev/hda doesn't contain a valid partition table
root@example.com:~# date;time dd if=/dev/zero bs=1M of=/dev/hda;date
Wed Aug 15 22:36:58 EDT 2007
dd: writing `/dev/hda': No space left on device
19093+0 records in
19092+0 records out
20020396032 bytes (20 GB) copied, 490.942 seconds, 40.8 MB/s

real    8m10.961s
user    0m0.212s
sys     2m47.522s
Wed Aug 15 22:45:11 EDT 2007
root@example.com:~# date;time dd if=/dev/zero bs=512 of=/dev/hda;date
Wed Aug 15 22:45:11 EDT 2007
dd: writing `/dev/hda': No space left on device
39102337+0 records in
39102336+0 records out
20020396032 bytes (20 GB) copied, 1841.85 seconds, 10.9 MB/s

real    30m41.875s
user    1m7.004s
sys     12m46.120s
Wed Aug 15 23:15:53 EDT 2007
root@example.com:~# date;time dd if=/dev/zero bs=1 of=/dev/hda;date
Wed Aug 15 23:15:53 EDT 2007
dd: writing `/dev/hda': No space left on device
20020396033+0 records in
20020396032+0 records out
20020396032 bytes (20 GB) copied, 45477.4 seconds, 440 kB/s

real    757m57.384s
user    174m58.672s
sys     569m33.912s
Thu Aug 16 11:53:52 EDT 2007
root@example.com:~#