On Thu, Mar 14, 2002 at 06:50:10PM -0800, Jim VandeVegt wrote:
"The best backup and restore practises" book from Sun recommends
to disable buffering in tape device's driver, as soon as
amount of data much large than buffers.
NetBackup is buffering
OS is buffering
Tape drive is buffering too.
How good it is I don't know.
With my setting:
Q-DLT7000 = 1,0x38,0,0x3D639,4,0x82,0x83,0x84,0x85,2;
allows me to write at 9 MB/s on 10 sec interval to DLT7000 tape drive,
which is even better than promissed by Quantum.
Thanks,
Andrew
>
> The fourth field of the DLT7K-data specification in st.conf is a set
> of flags. The flag assigned to 0x4000 is ST_BUFFERED_WRITES. I think
> that probably should be "on" for better tape drive performance, and
> this thinking is supported in the 'st' man page.
>
> Later on in the same man page, however, it seems to outline two more
> parameters that, if not set, default to *no* write buffering.
>
> The "tape-driver-buffering" parameter is set to the number of write
> requests to buffer. If not set, the man page says it defaults to 0.
> Wouldn't setting the limit on the number of write requests to buffer
> to zero effectively disable write buffering?
>
> The other parameter is "tape-driver-buf-max-size" and it defaults to
> 1MB.
>
> The st man page goes on to state that if write buffering is to
> operate properly sufficient space must exist on the media after LEOT
> in order to flush the
> remaining data to tape. How much media space is left when DLT7K
> signals LEOT?
>
> Has anyone set the "tape-driver-buffering" and
> "tape-driver-buf-max-size" parameters in addition to
> ST_BUFFERED_WRITES in their st.conf file? Noticed any performance
> improvements or problems?
>
> =====
> Jim VandeVegt
> vandevegt AT yahoo DOT com vandevegt AT avaya DOT com
> http://members.xoom.com/vandevegt
> There is no luck except where there is discipline.
>
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--
----
Andrew Shinkarev
Network Systems Specialist
Abbott Laboratories
(847) 9387559
shinkara AT pprd.abbott DOT com
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