[clug] Neat Backup Solutions for desktops...

steve jenkin sjenkin at canb.auug.org.au
Tue Dec 8 01:18:07 MST 2009

Sam Couter wrote on 8/12/09 6:28 PM:
> Daniel Pittman <daniel at rimspace.net> wrote:
>> "Alastair D'Silva" <alastair at newmillennium.net.au> writes:
>>> One problem with streaming encryption is that if you have any data
>>> corruption, data from that point on is lost.
>> Most of the encrypting done via a pipe is "streaming" only by choice, because
>> you selected an inappropriate feedback mode.  You could use a mode like ECB
>> that trades off some types of security in return for per-block protection.
> What he said.
> Also, compression usually has the same risk, where the compressed stream
> is invalid after the corrupted byte.
> In Amanda's case, each filesystem is compressed and encrypted
> separately, so other filesystems on the same media won't be corrupted by
> one stray cosmic ray.

In my professional life, I can't remember once when I was able to
recover from backups easily/simply - sometimes, or at all.
This includes using commercial products & server-grade drives/media.

In 2003 I collected "war stories" about backups from a Sys Admin list.

In spite of extreme efforts, after 3-5 years media were found unrecoverable:

- 'A' wrote 3 optical disks on separate m/c, swap drives & verify (md5).
  Common faulty media blamed. Bad batch or dodgy manufacturer?

- 'B' wrote two copies, one to optical disk, another copy to DLT.
  Both media unreadable.


I'll second Sam, "what they said".
Easy to write data, harder to get it back.

Steve Jenkin, Info Tech, Systems and Design Specialist.
0412 786 915 (+61 412 786 915)
PO Box 48, Kippax ACT 2615, AUSTRALIA

sjenkin at canb.auug.org.au http://members.tip.net.au/~sjenkin

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