topic Re: Script to Create 600MB file in Operating System - HP-UX

Script to Create 600MB file

Nikee Reddy — Thu, 12 Aug 2004 13:16:26 GMT

Hello,

We are planning to transfer some of the dump data (600MB each file approx. 80GB data) from US to Europe using the FTP protocol.

Before we do this task, we have decided to perform some test data transfer.

Can you give me some script to create some test data in a file of size 600MB?

Example:
Touch data1.ftp
if the file size < 600MB
then
Add "this is line 1" >> data1.ftp
else
echo "File created of size 600MB"
endif.

Thanks,
Nikee

Re: Script to Create 600MB file

Jeff_Traigle — Thu, 12 Aug 2004 13:22:28 GMT

Use the prealloc command to create files of a given size. No need for scripts on this one unless you're going to make a lot of said files all at once. :)

Re: Script to Create 600MB file

Patrick Wallek — Thu, 12 Aug 2004 13:24:40 GMT

Use prealloc to create a 600MB file.

# prealloc 600MBFile 629145600

Note that prealloc uses the number of BYTES for the file size.

Re: Script to Create 600MB file

Hein van den Heuvel — Thu, 12 Aug 2004 13:32:50 GMT

dd bs=1024K count=600 if=/dev/null of=your-big-file

Or if=/dev/random if you have that?

Or if=/dev/rdsk123

Or if=/oracle/data/somebigfile.dbf

Hein.

Re: Script to Create 600MB file

Alzhy — Thu, 12 Aug 2004 13:40:45 GMT

If you are going to do some benchmarking (and will be using some compression on both ends) - then "prealloc" created file will not do justice.

Use either:

dd if=/dev/random of=data1.ftp bs=8k count=76800

or dd if=/oramount/dbinstance.dmp of=data1.ftp bs=8k count=76800

HTH.

Re: Script to Create 600MB file

Jeff Schussele — Thu, 12 Aug 2004 13:44:21 GMT

Hi Nikee,

I'm not sure a prealloc file will do the trick for you. It's what's termed a sparse file & ftp *may* not send all the null space between the start & ending block. And if it does, sending all zeroes won't be a real world test.
A better idea maybe to use dd to read any old disk with more than 600MB of data on it & write it to a file - like:

dd if=/dev/dsk/cXtYdZ of=/path/to/600mb_file bs=512k count=1200

Rgds,
Jeff

Re: Script to Create 600MB file

A. Clay Stephenson — Thu, 12 Aug 2004 14:01:52 GMT

The read() system will definitely fill in the NUL's for a sparse file and will send it all 600MB's of NUL's. ANY application will treat the read of a sparse file like that including backup programs like fbackup, OmniBack (DataProtector), and Netbackup. Note that all of these can restore a sparse file (though possibly not precisely as it was) but that do that on the restoring side. The restores do it by noting that a whole herd of NUL's has been seen so that lseeks() are done within the file to "re-sparse" the file.

Re: Script to Create 600MB file

Nikee Reddy — Thu, 12 Aug 2004 14:02:16 GMT

Hello All,

Thanks for the quick response.

Well, if I use the dd command, how can I verify the file after the FTP transfer?
I mean, data is good inside the file and the
checksum is good and the integrity?

Thanks,
Nikee

Re: Script to Create 600MB file

Alzhy — Thu, 12 Aug 2004 14:35:47 GMT

You can use cksum, md5.. whatever suits you..