> > It wouldn't help you recover, but you would be able to report that 
> > you cannot recover.
> 
> How? The scenario Vadim is pointing out is where the disk 
> drive writes a changed data block in advance of the WAL log entry
> describing the change. Then power drops and the WAL entry never gets
> made. At restart, how will you realize that that data block now
> contains data you don't want? There's not even a log entry telling
> you you need to look at it, much less one that tells you what should
> be in it.
> 
> AFAICS, disk-block CRCs do not guard against mishaps involving intended
> writes. They will help guard against data corruption that might creep
> in due to outside factors, however.

I couldn't describe better -:)

Vadim

Fri, 12 Jan 2001 15:14:50 -0800
"Mikheev, Vadim" <vmikheev@SECTORBASE.COM>
RE: CRCs 