[Novalug] need dd help

Jay Hart jhart@kevla.org
Tue Feb 14 07:26:45 EST 2012


For the second disk, I up'ed bs from 1k to 1M. Look at the difference:

[jay@freenas] /dev/ufs# dd if=/dev/zero of=/dev/ada0 bs=1k
dd: /dev/ada0: end of device
976762585+0 records in
976762584+0 records out
1000204886016 bytes transferred in 85322.193527 secs (11722681 bytes/sec)

[jay@freenas] /dev/ufs# dd if=/dev/zero of=/dev/ada1 bs=1M
dd: /dev/ada1: short write on character device
dd: /dev/ada1: end of device
953870+0 records in
953869+1 records out
1000204886016 bytes transferred in 10792.327848 secs (92677400 bytes/sec)

Hugh difference in completion time.

Jay

> On Mon, Feb 13, 2012 at 07:46:55PM -0500, Jay Hart wrote:
>> Ok,
>>
>> [jay@freenas /]$ iostat
>>        tty             da0             ada0             ada1             cpu
>>  tin  tout  KB/t tps  MB/s   KB/t tps  MB/s   KB/t tps  MB/s  us ni sy in id
>>    0     1  5.39   0  0.00   1.00 11094 10.83   2.17   0  0.00   2  0 45 23
>> 30
>>
>> What does this mean???
>>
> Jay, I won't interpret it, but only point out that you need to
> add an interval time, and possibly a count argument, to get
> multiple reports.  For both vmstat and iostat the first report
> is data since the last reboot.
>
> $ iostat 2 3
> Linux 3.2.5-3.fc16.x86_64 (vost.jgcomp.com)  02/13/2012  _x86_64_  (2 CPU)
>
> avg-cpu:  %user   %nice %system %iowait  %steal   %idle
>            0.56    0.10    0.83    0.01    0.00   98.50
>
> Device:            tps    kB_read/s    kB_wrtn/s    kB_read    kB_wrtn
> sda               0.90        16.36         8.73    1242018     662852
>
> avg-cpu:  %user   %nice %system %iowait  %steal   %idle
>            2.00    0.00    2.00    0.00    0.00   96.00
>
> Device:            tps    kB_read/s    kB_wrtn/s    kB_read    kB_wrtn
> sda               3.50         0.00        42.00          0         84
>
> avg-cpu:  %user   %nice %system %iowait  %steal   %idle
>            1.76    0.00    1.51    0.00    0.00   96.73
>
> Device:            tps    kB_read/s    kB_wrtn/s    kB_read    kB_wrtn
> sda               1.00         8.00         0.00         16          0
>
>
> --
> Jon H. LaBadie                  novalugml@jgcomp.com
>  11226 South Shore Rd		(703) 787-0688 (H)
>  Reston, VA  20190		(609) 477-8330 (C)
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