Re: shadowing (like IB/Firebird)

On 4/26/04 3:25 PM, "Glen Parker"  wrote:

> Sounds an aweful lot like RAID level one :-)  Why would a DB system need to
> do what RAID already does quite well?

One case I can think of is where the shadow is on a separate system (e.g. a
SAN or NetApps, another linux box, etc.).  RAID doesn't protect you against
certain types of hardware failure.  We recently lost a RAID 5 due to a
double disk failure.  We've had high end boxes lose a RAID when just one
disk went out (theoretically shouldn't happen) - apparently when the disk
died it caused corruption elsewhere.  I have also seen (a couple of times) a
controller go bad and proceed to write garbage all over the disks.  The
mirroring worked quite well - we had a very nice file system full of
mirrored garbage.

Of course, none of these protect you against an errant application that did
a 'delete from' instead of 'delete from where'...

Wes