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

The deleted records would be saved. I don't know if the
compression/compaction algorithms take a record's deleted status into
account - I think they would not, so the space taken up by a deleted
record would be taken up on tape also.

> -------- Original Message --------
> Subject: RE: determine how full a tape is
> From: "phil Kestenbaum" <pkestenbaum@xxxxxxxxx>
> Date: Tue, November 15, 2005 8:39 am
> To: "Midrange Systems Technical Discussion" <midrange-l@xxxxxxxxxxxx>
> 
> 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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