How long should dd take?

[GBR]

I'm running this command:

dd if=/dev/dsk/c2t0d0 of=/dev/null bs=2048k

How long should it take?

GBR

[TwoProc]

Well, that depends on how big the disk is.
HOWEVER, it would run 5 to 8 times faster if you used the raw interface instead of the block.

dd if=/dev/rdsk/c2t0d0 of=/dev/null bs=2048k

[GBR]

18 GB is the size. The command has been running for like 20 minutes. I'm guessing it shouldn't take this long?

GBR

[Tim Nelson]

Based on the following factors.

size of disks
speed of disks
type of disks
configuration of the disks
speed of the interface
skipping the buffer
....
....
....

A swag for a 36GB 15K SCSI-2 disk is about 20-30 minutes

[John Guster]

put count=10 after bs=2048k depend on what test you want.

[GBR]

I want to test hard drive corruption.

[TwoProc]

Well, 20 minutes may or may not be how long it takes, but you're using the slowest interface.
Use /dev/rdsk/xxxxx instead of /dev/dsk/xxxxx

For whatever reason, the block interface for doing "dd" commands is much slower.

[TwoProc]

On an RP7410,

I'm running the command:

$> time dd if=/dev/rdsk/c3t6d0 of=/dev/null bs=2048 count=9216

I'll let you know what it says when done...

It's ~probably~ a U160 SCSI drive running at 10K rpm; that's from what I remember anyways...

[TwoProc]

$> time dd if=/dev/rdsk/c3t6d0 of=/dev/null bs=2048k count=9216
9216+0 records in
9216+0 records out

real 5:29.2
user 0.0
sys 3.1

So, that's 18G in 5 1/2 minutes using /rdsk/
interface...


I'm now running it from /dsk/ instead of /rdsk/

[TwoProc]

Wow, it's been a Looong time since I pulled data from the slower interface - apparently, it's not nearly as bad as I remember... :-)

Here's the final data for pulling 18G from a disk into /dev/null 2M at a time...

$> time dd if=/dev/rdsk/c3t6d0 of=/dev/null bs=2048k count=9216
9216+0 records in
9216+0 records out

real 5:29.2
user 0.0
sys 3.1
$> time dd if=/dev/dsk/c3t6d0 of=/dev/null bs=2048k count=9216
9216+0 records in
9216+0 records out

real 6:26.5
user 0.1
sys 2:09.8


So, to finally answer your question: 6 and 1/2 minutes

- sorry about all the info you apparently weren't interested in (rdsk)...

[GBR]

Thanks.