> I'd like to say that I am not knocking Retrospect in the very least.
> This discussion on compression started by a feature suggestion.
> Retrospect is the best backup software on the market. I say that
> without hesitation because our department has tried at least 2 others
> and they quite fra
> I am very familiar with how modem compression, network compression,
> and file compression works. When I was going through school, one of
> our projects was to write a compression algorythem and compress a
> file (yes, it was a text file) the best we could. With my limited
> math background, I
I'd like to say that I am not knocking Retrospect in the very least.
This discussion on compression started by a feature suggestion.
Retrospect is the best backup software on the market. I say that
without hesitation because our department has tried at least 2 others
and they quite frankly su
> Could someone techy from Dantz weigh in on this?
Wow -- where to begin?
1. Retrospect only copies unique files to the backup set, which does reduce
the amount of data copied to the backup set without reducing safety.
Typically, you can expect to only copy 70-80% of the data on a network,
depe
Could someone techy from Dantz weigh in on this?
I think some of the participants in this discussion have hit on some of
the key issues, but it seems like someone from Dantz could clarify a lot.
It seems that the distinctions between streaming a compressed file at a
time for an indeterminate num
At 11:46 PM +0100 21/10/00, Nicholas Froome wrote:
>
>>Ok, explain to me...I took a 220MB system file and compressed it
>>down to 28MB.
>
>And to recover any one file would require the whole archive to be
>decompressed..
Actually that is NOT true. Every compression/archive utility that I
have
>Reality check, I've been getting about 27GB onto a 20GB/40GB drive.
>This is typical. You should be able to get 17-18GB on the drive on
>average.
Par for the course. We get 33-36 GB on our 25 GB native AIT tapes.
>Warning, my rant follows:
>
>What I don't get is that they have not improved t
> Ok, explain to me...I took a 220MB system file and compressed it down to 28MB.
Must have had a lot of repeating data. Text files, etc... Also was that
220MB of allocated space or used space. I'd bet the former.
> Obviously this is lossless as I can recover individual files from
> within it tha
> >Ok, explain to me...I took a 220MB system file and compressed it
>down to 28MB.
>
>And to recover any one file would require the whole archive to be
>decompressed..
Actually, if you buy the full version of StuffIt Deluxe, it can
retrieve individual files and add files to the end of it as w
Dantz has being supporting Retrospect since the days when backups were
done to stacks of diskettes (and NOT 2HD either). The issue of compression
efficiency has been agonized over almost as much as Peace in the Middle East.
A number of years ago the tape industry finally arrived at a gentleman's
>Ok, explain to me...I took a 220MB system file and compressed it down to 28MB.
And to recover any one file would require the whole archive to be decompressed..
Compressing a finite amount of data is one thing. Compressing a potentially infinite
amount of data on the fly, to multiple media, wit
Ok, explain to me...I took a 220MB system file and compressed it down to 28MB.
Obviously this is lossless as I can recover individual files from
within it that are things like extensions, fonts, etc.
I admit, JPEG, MPEG, etc. are lossful, but modems have been doing
v.42bis compression which is
One (compound) word: Lossless
The compression methods that you are lusting after introduce errors
(artifacts) into the resulting decompressed data. This may be acceptable
for sound, photos and video but to totally unacceptable for storage of
system files, programs and most other data.
High level
information in the JPEG file simply doesn't
exist.
Brad.
-Original Message-
From: Matt Barkdull [mailto:[EMAIL PROTECTED]]
Sent: Friday, October 20, 2000 1:15 PM
To: retro-talk
Subject: Re: tape capacity
One word: Compression.
Native capacities are with no compression. For examp
"Native" is the actual amount of data that the tape can theoretically store,
before compression. A 12.0 Gig file should fit on a 12.0 Gig capacity tape.
Suppose you are able to take a 16.0 Gig file and compress it down (using
PKZIP or whatever) to 12.0 Gigs. Now that 16.0 Gig file can fit on the
One word Matt: Compression
Native capacity is the amount of uncompressed data that will fit on the tape.
The drive has a hardware-based compressor that squeezes the data as it streams
from the SCSI port to the write mechanism.
The amount the data gets compressed depends upon the characteristi
One word: Compression.
Native capacities are with no compression. For example, your 12GB
drive can hold up to 12GB of un-compressed data. Normal hardware
compression can get up to 2:1 compression, giving a total maximum of
24GB.
Reality check, I've been getting about 27GB onto a 20GB/40GB
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