RE: determine how full a tape is -- MIDRANGE-L

If a file has deleted records, they absolutely get saved to tape.

Al

Al Barsa, Jr.
Barsa Consulting Group, LLC

400>390

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In line w/ this, I was wondering if there is a PF that has deleted records
on it, do they get saved to tape as well, whatever space they occupy on
Disk, does this get transferred to tape in full?

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx]On Behalf Of
qsrvbas@xxxxxxxxxxxx
Sent: Monday, November 14, 2005 11:38 PM
To: midrange-l@xxxxxxxxxxxx
Subject: RE: determine how full a tape is


midrange-l-request@xxxxxxxxxxxx wrote:

>   1. determine how full a tape is (Jim Franz)
>
>date: Fri, 11 Nov 2005 09:20:33 -0500
>
>Is there a command or any other way to determine how full (a percentage?)
>a cartridge tape is? Customer's backup is a single cartridge, and I am
>preparing to add a large set of files. Need to see if nightly unattended
backup
>will ask for 2nd tape. This is SLR60 tapes. Any formula w/block length and

>file length from dsptap report?


I haven't looked into this for years. Back then, the unknown variable was
the size and number of inter-record gaps -- the unused space between the
end of one record/block on the tape and the start of the next. Gaps could
simply be between blocks within a tape file or between file, possibly
between the various file markers and the files, I'm not sure.

I'd swear that when I was looking into it, the storage density of tapes had
reached the point where there was often more space in the gaps than in the
actual data written to tape for many small files.

Because the ratio of gaps-to-data had gotten close to 1.0 in some cases,
estimating how much "space" was left got to be tricky. You might store 1GB
more on a tape if it was hundreds of small documents or 5GB if it was a
single large file. (Exaggerating... maybe?)

In months/years after, tape technology got so complex, I didn't even try to
search such things out anymore. Maybe somebody knows a site that has good
_useful_ info.

Tom Liotta

--
Tom Liotta
The PowerTech Group, Inc.
19426 68th Avenue South
Kent, WA 98032
Phone  253-872-7788 x313
Fax    253-872-7904
http://www.powertech.com


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