On Thursday 28 September 2006 08:16, McGraw, Robert P. wrote:
>My default chunk size is CHUNKSIZE 1048576.

A megabyte is pretty small.  I believe most use something on the order of a 
gigabyte if using it at all.  This was originally used only as a bandaid 
to get around those filesystems with a 2GB maximum file size limit on the 
disk. 

>How do the tapers write the chunks that are on the holding disk? Does it
>combine them into one file before writing or does it concatenate the
> chunks on the fly. Or what kind of magic does it do to get the data to
> tape.

I believe its concatenated on the fly.

>Does this process slow down the streaming of the data to tapes? 

At 1 megabyte, I'd guess it might effect the writing speed slightly. It 
would depend on the ability of the filesystem to keep the drives buffer 
filled well enough that the drive doesn't have to write a lot of null 
blocks because it ran out of data.  This would also impinge on the tapes 
apparent capacity.

>I have a 
>large holding disk, would I benefit from larger chunksize?

If your filesystems have no problems with a tarball of your largest DLE, I 
wouldn't use it at all.
>
>
>Thanks
>
>Robert
>
>
>_____________________________________________________________________
>Robert P. McGraw, Jr.
>Manager, Computer System                 EMAIL: rmcgraw AT purdue DOT edu
>Purdue University                         ROOM: MATH-807
>Department of Mathematics                PHONE: (765) 494-6055
>150 N. University Street                   FAX: (419) 821-0540
>West Lafayette, IN 47907-2067

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