Slides from May talk now available

[Robert Brockway]

On Mon, 18 May 2009, Ken Burtch wrote:

> I hope "Don't backup ... use RAID 1" was not referring to my blog entry
> a couple of months ago.

No, it wasn't :)  People have said this to be a few times but I was 
principally thinking about a discussion at a party many years ago.

Yes, I talk about backup strategies at parties ;)

> Just to be clear (if it was me): I was talking about data
> integrity...ensuring corrupted files aren't written to the backup.  With
> modern drives and terabytes of data that lingers for years, that photo
> of your mom you took 10 years ago getting corrupted is a real problem.
> I've got Apple II files that I can no longer generate sitting on my
> website and they are irreplaceable.  Any one of them could get ruined by
> a single bad block but would still be blissfully written to a backup
> disk or tape without anyone being the wiser.  I don't know why a thread

These are some good points.

One option is to keep md5 hashes of files and use them to verify the 
backups.   This is not something I've put in my custom backup system yet 
but perhaps I should.

> For disaster recovery, I think that the most critical point one could
> make is that making backups is useless if you can't restore from them,
> so a practice restore is always required to ensure the the backups are
> backing up the right information and in a usable form for recovery.

Absolutely.  Disaster Recovery Testing (DRT) is an essential component of 
a backup strategy.

As I noted during the talk I plan this stuff out, do DRT and I've still 
found problems to solve when a real DR came about.

> Backup up the database directory, while the database is actively
> running, is a good example of getting data in a form that cannot be used
> for recovery.  This may not be realized until a restore is attempted.

A question during the talk focused on this exact issue.

Cheers,

Rob

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