Re: star tape I/O suggestion

[email protected] wrote:

> The default blocking factor of star (and other tar programs) is 20, so
> data is written in chunks of 10240 bytes.
>
> While using that small a tape block size allows for wider interchange,
> writing one block at a time gives lower performance than necessary. When
> writing to tape, the user can set fixed block size mode, e.g. by doing
>   mt -f /dev/nst0 setblk 10240
>
> Each tape I/O can then be a multiple of the block size, rather than a
> single block. On my system the Linux kernel imposes an arbitrary limit on
> I/O length of 512KB. But that would still allow each I/O to be of 51
> 10240-byte blocks.
>
> It would thus improve performance if star were able to, when writing to
> tape, write in chunks of 51 blocks (in this example). The final write
> would be for a lower number of blocks. The same could apply for reading
> from tape.

Star is able to write any blosk size sou like in case your OS suppoorts thi=
s.

Just specify the block size you need. Note that writing blocks that are lar=
ger =

than 63 kB may cause you top become unable to read in tapes on some OS or =

hardware.

The drive needs to have a suffucient amount of RAM, the DMA controler needs=
 to =

support a DMA counter that sopports the desired DMA count and the OS needs =
to =

support this too.

J=F6rg

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