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Re: jkhv (Sector by Sector Backup)

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Paul <nospam@needed.invalid> wrote in news:r7o4um$64b$1@dont-email.me:

> Boris wrote:
>> Why does Acronis True Image, the free Western Digital Edition, have the
>> option to do partition image backups, sector by sector.  The default is
>> to have this option disabled, but if enabled, there is a sub-option to
>> include all unallocated disk space?
>> 
>> https://postimg.cc/tsFcLjwd
>> 
>> So what does the default setting do?
>> 
>> And, I read a while ago that sector by sector eliminates any
>> compression?  True?
>> 
>> Thanks. 
> 
> Backing up sector by sector, where unallocated are not captured,
> replaces unallocated with zeros. If the program supports GZIP style
> compression, the zeros portion compresses to nothing. 20GB of
> files on a 1TB drive can then be stored in <20GB of space
> (compressible). Nothing prevents a compressor from compressing any
> "stream" of data, if that's what you want.
> 
>            <------ 20GB disk reads, to get this ---------> <- no reads
>            this part  -> 
>                                                               (faking
>                               this part) 
>                                   LBA
>            <--------------------------------------------->
>            sectr|sectr|sectr|sectr|sectr|sectr|sectr|sectr
>            000000000000000000000000 
> 
>            <---- compress the whole pattern, including the fake part,
>            then write --> 
>                  could be less than 20GB total writes
> 
>            If image is ever "exported", then the program pretends that
>            1TB worth of sectors are available.
> 
> In the case of ticking the "please capture the unallocated", this
> would also be termed a "forensic copy". It allows a person with
> an "unerase" program, to flip the byte in the $MFT that marks
> a file as erased, and set it back to the unerased state, and then
> the file can be both seen and read. The pattern in this case, looks as
> follows. The compressor can run if it wants. *But*, because
> the unallocated is not just random stuff pulled off the disk, the
> 20GB of files stored on the 1TB drive now takes 400GB of (compressed)
> storage. The compression is lossless, and probably isn't all that
> compressible. 
> 
>            <----------- disk reads for the whole thing
>            ------------------------------> 
> 
>                                   LBA
>            <--------------------------------------------->
>            sectr|sectr|sectr|sectr|sectr|sectr|sectr|sectr
>            13572468ACEFBD0045671234... 
> 
>            <---- compress everything, write it out compressed
>            -----------------------> 
>                  pattern might not be very compressible

Acronis instructions state, "By default Acronis True Image stores only the
hard disk sectors that contain data". 

The Acronis Help that I quoted in the OP made me wonder what happens when
the sector by sector box is selected, but not the 'unallocated space' box.
 Seems to me that the only option needed is something like 'enable backup
of unallocated space'. 

On the other hand, Macrium Reflect allows backing up of unallocated space
for forensic purposes, and at the same time, offers levels of compression.

https://postimg.cc/yW11tTjD

I'm not concerned about forensics, but guess it's possible with
compression. 

Seems the devil's in the details, for those who need to know how each
product acts. 


> 
> If you're the kind of person who zeros your drives before first
> usage, even when you tick the "capture unallocated" option, the
> output may still have a significant number of zeroed LBAs and
> it compresses nicely.
> 
> Find a small disk, and you should be able to verify these
> behaviors a bit faster. I don't know what the Acronis
> export options are, or how easy it is to verify what
> got captured.
> 
> The smallest WD disk I've got is 4GB :-) It has a piss poor
> read/write rate. But it might be good enough to fool the
> Acronis branding check that it's a WD disk. The slowness of the
> disk, negates the small size, so it's not particularly
> attractive to hook to the computer in 2020.

I could look around, but the smallest WD I know I have is an 80GB in a
Vantec case (and in use). 


> 
>     Paul

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Thread

jkhv Boris <nospam@nospam.invalid> - 2020-04-22 00:29 +0000
  Re: jkhv Paul <nospam@needed.invalid> - 2020-04-21 21:00 -0400
    Re: jkhv Char Jackson <none@none.invalid> - 2020-04-21 20:14 -0500
      Re: jkhv (Sector by Sector Backup) Boris <nospam@nospam.invalid> - 2020-04-22 03:00 +0000
        Re: jkhv (Sector by Sector Backup) Boris <nospam@nospam.invalid> - 2020-04-22 20:18 +0000
    Re: jkhv (Sector by Sector Backup) Boris <nospam@nospam.invalid> - 2020-04-22 02:30 +0000
      Re: jkhv (Sector by Sector Backup) Paul <nospam@needed.invalid> - 2020-04-22 02:08 -0400
        Re: jkhv (Sector by Sector Backup) Boris <nospam@nospam.invalid> - 2020-04-23 03:09 +0000
          Re: jkhv (Sector by Sector Backup) Paul <nospam@needed.invalid> - 2020-04-22 23:34 -0400

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