IO Error using dd

[Bugs_Bnny]

Hi ALL,

I am using dd to transfer data between two logical volumes in two diff VG's and I am getting the following error
"I/O Error"
20001+0 records in
20000+1 records out

why does this error occur , how can i fix this , the disks are fine as I do not see any scsi errors in my syslog or dmesg.
Thanks in adv,
Bugs_Bnny

[Pete Randall · Accepted solution]

What's up doc?

Anyway, does vgdisplay show the two VG to be identical in number and size of PE's?

Pete

[Pete Randall]

And what are you using for a block size on your dd command?

Pete

[RAC_1]

dd does block by block copy.
if it is saying i/o error, then check with fsck on both lvols.

[Paul Sperry]

Looks like the source or destination hard disk has bad blocks. Use the command
dd if=/dev/rdsk/c0t1d0 of=/dev/null bs=1024k, to check to see if the command gives the same I/O Error.
Once again it depends whether the HDD is used as a physcial volume or it is a raw disk. If it is a physical volume and is part of a volume group, the lvm subsystem will take care about bad block relocation.

[A. Clay Stephenson]

You need to do an echo ${?} immediately upon the exit of dd to indicate the errno BUT it appears that you have reached the end of the lvol on the destination. The '+ 0' means that no partial blocks were read but the '+ 1' indicates that a partial block was written. If you are going to do this kind of transfer, you need to make certain that the destination is at least as big as the source. I would also specify a rather large blocksize (e.g. bs=8000k) to speed the process.

[Marco Santerre]

I was just about to mention to make sure that your destination Logical Volume has the same number of extent as your Source Logical Volume.

[Eugeny Brychkov]

This error you receive is most probably means that source volume has more physical extents than destination can keep (Pete is right). So dd did not finish reading source volume, but destination volume appeared reached its end
Eugeny

[Bugs_Bnny]

Thanks ALL !

The destination lvol was smaller than the source lvol. Thank you for all your responses. I have assigned apporpriate points to everybody.

Reagrds,
Bugs_Bnny