topic Re: DD and blksize in Operating System - HP-UX

DD and blksize

Dario_1 — Wed, 13 Mar 2002 21:16:13 GMT

One of my disk drives crashed today and I am planning on using the dd command to copy the information to the new drive. I want to know if the blksize number would make a different in the speed of the process. If so, which one do you thing it would be the best blksize number I should use to do this proccess faster?

Tkx, Dario

Re: DD and blksize

Michael Tully — Wed, 13 Mar 2002 21:24:58 GMT

Hi,

Where is the information currently stored ?

Was the disk mirrored?

Re: DD and blksize

Dario_1 — Wed, 13 Mar 2002 21:33:21 GMT

After it crashed this morning I was able to bring the machine back up and we were using the disk for 5 hours and it crashed again. It is running now but HP will bring a new disk. What I want to do is, use the dd command to copy all the information to it without having to restore from tape. Would this be possible?

Thank you again.

Re: DD and blksize

Michael Tully — Wed, 13 Mar 2002 21:53:40 GMT

Given that this disk is already dodgy I would use the tried and proven method of tape first.
Make sure that you have a backup! Sometimes
yes this is slower, but less risky. Then by all means if the disk is still alive when the a new one is plugged in you go ahead and do a 'dd'.

Re: DD and blksize

Dario_1 — Wed, 13 Mar 2002 22:01:28 GMT

Thank you Michael for your answer. We already have the set of backup tapes ready and I am also running a last backup just in case. I the use of the dd command will allow us to do the copy faster than the restore. Thank you again.

Regards, Dario

Re: DD and blksize

melvyn burnard — Wed, 13 Mar 2002 22:14:40 GMT

The bigger the block size, the faster this will copy.
However, remember that dd is a bit-by-bit copy, and it will copy rubbish over if that is what is there, there is NO error checking.
If you are prepared to try this, then set a block size something like bs=1024k

Re: DD and blksize

Dario_1 — Wed, 13 Mar 2002 23:08:15 GMT

Guys:

The other backup is done. I will be copying the information using the dd with a bs=1024, let see if it works.

As always, thank you for your help.

Regards, Dario