topic Blocking factor on tar in Operating System - HP-UX

Blocking factor on tar

Scott Dunkley — Wed, 28 Jul 2004 03:42:48 GMT

I have obviously misunderstood the use of the blocking factor on tar. I am having problems with slow DLT drives and one sugegstion is to up the blocking factor to 64. Now to me that makes sense 64*512 bytes is 32k and thats the size block I am trying to get to. However when I run tar -b64 -cvf /dev/rmt/0m .....

I get Invalid blocksize. (Max 64)

Isnt my blocksize 32 when using a blocking cator of 64?????

Re: Blocking factor on tar

Steve Steel — Wed, 28 Jul 2004 03:57:44 GMT

Hi

Try

tar -cvf /dev/rmt/0m -b 64

Steve Steel

Re: Blocking factor on tar

Scott Dunkley — Wed, 28 Jul 2004 04:01:21 GMT

Ok so I tried it that way:

$ tar -cvf /dev/rmt/0mn -b 64 /etc/hosts
tar: cannot stat -b. Not dumped.
tar: cannot stat 64. Not dumped.
a /etc/hosts 2 blocks

It tries to backup a file called -b a 64 so I put the -b 64 or -b64 at the end like:

$ tar -cvf /dev/rmt/0mn /etc/hosts -b64
a /etc/hosts 2 blocks
tar: cannot stat -b64. Not dumped

and it still tries to backup a file called -b64 or -b and 64.

any other suggestions.

Re: Blocking factor on tar

S. Singaravelu — Wed, 28 Jul 2004 05:16:33 GMT

hi

Block size cannot be more than 20. Check out the man page for blocking factor.

rgrds
[V]

Re: Blocking factor on tar

Scott Dunkley — Wed, 28 Jul 2004 05:22:06 GMT

yes it can it can be upto 64 and this is what I have been advised to try by HP to get round the slow speed of tar on DLT8000 using latest firmware. 64 is the maximum.

I have got it to work but not with the -f option as well. If I do:

tar -cvb 64 /etc/hosts

it works ok and backups to the default /dev/rmt/0m location but when you try and add in a non default destination using -f this is when I hit the issues highlighted.

Re: Blocking factor on tar

Scott Dunkley — Wed, 28 Jul 2004 05:33:07 GMT

Ok I have worked it out after reading the man page 3 or 4 times I now understand.

tar -cvfb /dev/rmt/0m 64 /etc/hosts

the order of the arguemnet list matters. Becuase the f is before the b the device file has to be before the blocking factor number.