This is an adendum to SUMMARY: size of savesets under AdvFS, compression
ratio.
Thanks to Ray Lauff, William Beelen, ABenthem_at_pvf.nl.
Disadvantages of
NSR (Networker): 1) The database created by NSR to track files can become
huge. Plan on about 1G of space if you are backing up
lots of files
2) NSR can't be used to restore system file systems, such
as root (/) and /usr, since it must be fully configured on
the system where it is being used before it works.
Size of savesets,
compression ratio: for DLT drives, there is a program 'dltcounter',
http://www.lnf.infn.it/~wolf/dlt/
shows bytes written, read, compression ratio.
tape exerciser, /usr/field/tapex, provides useful info
about data on tape.
> Thanks to
>
> Ronald D. Bowman
> alan_at_nabeth.cxo.dec.com
>
> Size of savesets: apparently, there is no simple way to find the size of
> the savesets on tape. Knowing the blocksize at which media
> was written it is possible to read back the file using 'dd':
>
> dd if=/dev/nrmt0h of=/dev/null bs=60k
>
> Knowing how many blocks are in a saveset it is possible to
> calculate the its size.
>
> Compression ratio: compare the size of the fileset and the corresponding sav
eset
> on tape.
>
> Advantages of NSR
> (Networker): creates a catalog of every backup: will tell you which tape
> the file you are looking for is on, sdpace to the saveset on
> that tape, and space to the records holding that file.
>
> can run multiple imput streams to a single output stream.
>
> can do network backups of client systems.
>
> supports media changes.
>
> H/w vs s/w
> compression: h/w (tape) compression is preferred to s/w (vdump) compressi
on
> (s/w compression uses CPU time). using both is most of the
> time wasteful as it may create additional overhead on tape.
Received on Fri Aug 07 1998 - 21:34:29 NZST