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#1 (**permalink**) 01-05-2008, 10:08 AM

Dear Friends,

Pls see below the output of the mksysb command I have run on a p52A
machine running AIX 5.3. It mentions a total size of 2580259756 bytes =
around 2.4 GB AND at the same time it also mentions "there are 3685376
blocks on 1 volumes" which is around 1.75 GB assuming a block size of
512 bytes.
I understand that there are 4 sections on the mksysb tape and the size
mentioned above is of the 4th section. Does this mean that around .7 GB
of data is written in the first three sections. It is hard to believe.
Could you please explain the discrepancy.

Thanks in advance.

Ashok Sangra

# tail sysbkp040806.txt
a 2 ./.rhosts
a 0 ./clonefs
a 7423 ./mbox
a 0 ./backup_verify
a 2513347 ./backup_verify/sysbkp040806.txt
a 0 ./proc
The total size is 2580259756 bytes.
Backup finished on Fri Aug 4 17:52:20 IST 2006; there are 3685376
blocks on 1 v
olumes.
0512-038 mksysb: Backup Completed Successfully.

#2 (**permalink**) 01-05-2008, 10:08 AM

Ashok Sangra wrote:
> Dear Friends,
>
> Pls see below the output of the mksysb command I have run on a p52A
> machine running AIX 5.3. It mentions a total size of 2580259756 bytes =
> around 2.4 GB AND at the same time it also mentions "there are 3685376
> blocks on 1 volumes" which is around 1.75 GB assuming a block size of
> 512 bytes.
> I understand that there are 4 sections on the mksysb tape and the size
> mentioned above is of the 4th section. Does this mean that around .7 GB
> of data is written in the first three sections. It is hard to believe.
> Could you please explain the discrepancy.
>
> Thanks in advance.
>
> Ashok Sangra
>
> # tail sysbkp040806.txt
> a 2 ./.rhosts
> a 0 ./clonefs
> a 7423 ./mbox
> a 0 ./backup_verify
> a 2513347 ./backup_verify/sysbkp040806.txt
> a 0 ./proc
> The total size is 2580259756 bytes.
> Backup finished on Fri Aug 4 17:52:20 IST 2006; there are 3685376
> blocks on 1 v
> olumes.
> 0512-038 mksysb: Backup Completed Successfully.

The block size of the 4th section is defined by the setting on the tape
drive at the time of the backup .. mt -f /dev/rmt# status or lsattr
-EHl rmt# will show you what it is set to.

if the blocksize is "0" then the 4th archive block size will be
512bytes.

Some tape drives do a certain amount of hardware compresion by default,
so this could account for the difference.

Why dont you restore each section using dd and add up the sizes ...

You could also use the tcopy command to see how much data is actually
on the tape as this command outputs data size on tape ..

HTH
Mark Taylor

#3 (**permalink**) 01-05-2008, 10:09 AM

Thanks Mark for clearing this.

I used tcopy to get info about the data stored on the tape. Precisely I
used tcopy /dev/rmt0 without a destination and it dumped the info on
the screen. The first section was about 14.5 MB, the second one was 5
MB anf the third one 512 bytes. But the total size of the data on the
tape was less than the actual size of data. This can be attributed to
compression, which I checked was enabled in my case.

thanks once again.

Regards,
Ashok Sangra

Mark Taylor wrote:
> Ashok Sangra wrote:
> > Dear Friends,
> >
> > Pls see below the output of the mksysb command I have run on a p52A
> > machine running AIX 5.3. It mentions a total size of 2580259756 bytes =
> > around 2.4 GB AND at the same time it also mentions "there are 3685376
> > blocks on 1 volumes" which is around 1.75 GB assuming a block size of
> > 512 bytes.
> > I understand that there are 4 sections on the mksysb tape and the size
> > mentioned above is of the 4th section. Does this mean that around .7 GB
> > of data is written in the first three sections. It is hard to believe.
> > Could you please explain the discrepancy.
> >
> > Thanks in advance.
> >
> > Ashok Sangra
> >
> > # tail sysbkp040806.txt
> > a 2 ./.rhosts
> > a 0 ./clonefs
> > a 7423 ./mbox
> > a 0 ./backup_verify
> > a 2513347 ./backup_verify/sysbkp040806.txt
> > a 0 ./proc
> > The total size is 2580259756 bytes.
> > Backup finished on Fri Aug 4 17:52:20 IST 2006; there are 3685376
> > blocks on 1 v
> > olumes.
> > 0512-038 mksysb: Backup Completed Successfully.
>
>
> The block size of the 4th section is defined by the setting on the tape
> drive at the time of the backup .. mt -f /dev/rmt# status or lsattr
> -EHl rmt# will show you what it is set to.
>
> if the blocksize is "0" then the 4th archive block size will be
> 512bytes.
>
> Some tape drives do a certain amount of hardware compresion by default,
> so this could account for the difference.
>
> Why dont you restore each section using dd and add up the sizes ...
>
> You could also use the tcopy command to see how much data is actually
> on the tape as this command outputs data size on tape ..
>
> HTH
> Mark Taylor

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size of data on mksysb tape