🚀 go-pugleaf

From Eric Schott, former product manager for DECnsr:

DECnsr uses in the 200-300 bytes per file stored in the index.  This
is going down in V2 vs. V1.

Since index size is directly related to the number of file entries stored
in the index, the trick is to try to limit the number of file entries
added.

With dump, tar, or cpio backup procedures, media tracking for recovering
files is very difficult (there are not tools to help...).  As such people
usually schedule backups on very short schedules, like full every week...to
limit the number of tapes I might have to search to find a file.


DECnsr does media/file tracking in the indexes, so lengthening backup 
cycles is an effective and efficient means to limit the volume of
data backed up, and the growth of the indexes.

Example:

   If a system has 200K files, with 6gb of storage.  Assume 5-15% of
the data is modified on a daily basis.

    A weekly schedule would backup approximately 10-12GB of data
    and 400K files per week.

    A monthly schedule would backup approximately 20-30GB a month
    with about 700-900K files.

    As you can see, the monthly schedule is almost half the "size"
    (measured in index and backup media/time).

    A quarterly schedule is even more efficient.

  The trick for longer schedules is:

    a) Be able to track the media for recovers automatically

    b) Schedule with overlapping backups, to minimize to potential
       data loss if a backup tape were destroyed.

    c) Smart recovery of "full" file systems...


Another assumption usually made, is recovers most likely happen from
backups made in the recent past (last 1-10 days).  DECnsr does support
purging of media from the index, and then "restoring" the media
to the index.

In short, don't apply dump/tar/cpio procudures blindly to a product
like DECnsr.  You will not be taking best advantage of the technology.

DECnsr also provides methods to do smart backups, like skipping
files, compress files, handling of swap files, that also provides
a method of reducing the volume of data/ number of files.

Eric
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