The dedup we are discussing is both what you are referring to as compression, (but far more than that) AND duplicate object elimination.

While this is not really a completely accurate description, the concepts are. Dedup of 40 to 1 would be the worst case. We see upwards of 100 to 1 often, with post dedup operations.

Jim Oberholtzer
Agile Technology Architects

On Jan 20, 2020, at 10:34 AM, Nathan Andelin <nandelin@xxxxxxxxx> wrote:


From the last few messages I gather that VTLs are defined as a tape media
library devices such that the "MLB" (i.e. WRKMLBSTS) and "TAP" (i.e.
INZTAP) commands work with them. Also, such that the behavior and options
in SAV, SAVLIB, and SAVOBJ that apply to tape media also apply to VTL
media. One might compare and contrast that with optical devices such as RDX
which are supported by alternate commands and command options. That was
what I was more interested in comparing and contrasting, although I
appreciate the distinctions that you've made regarding VTL media and mylar

When compared to mylar media, I also view RDX devices and media as a huge

I question your assertion that deduplication would reduce a say 1 TB
library to 20 GB on a VTL. That type of reduction sounds more like
compression than deduplication. My understanding is that deduplication
refers to the elimination of duplicate files. With optical media you
eliminate duplicate files by replacing them will current versions, rather
than adding new files during a save. You do that via the use of "labels".
Compression is also supported on optical media.
This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing list
To post a message email: MIDRANGE-L@xxxxxxxxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
or email: MIDRANGE-L-request@xxxxxxxxxxxxxxxxxx
Before posting, please take a moment to review the archives

Please contact support@xxxxxxxxxxxx for any subscription related questions.

Help support by shopping at with our affiliate link:

As an Amazon Associate we earn from qualifying purchases.

This thread ...


Follow On AppleNews
Return to Archive home page | Return to MIDRANGE.COM home page

This mailing list archive is Copyright 1997-2022 by and David Gibbs as a compilation work. Use of the archive is restricted to research of a business or technical nature. Any other uses are prohibited. Full details are available on our policy page. If you have questions about this, please contact [javascript protected email address].

Operating expenses for this site are earned using the Amazon Associate program and Google Adsense.