> > So, for what CRC could be used? To catch disk damages?
> > Disk has its own CRC for this.
>
> Oh, I see. For anyone else who has trouble reading between the lines:
>
> Blocks that have recently been written, but failed to make it down to
> the disk platter intact, should be restorable from the WAL log. So we
> do not need a block-level CRC to guard against partial writes.
>
> A block-level CRC might be useful to guard against long-term data
> lossage, but Vadim thinks that the disk's own CRCs ought to be
> sufficient for that (and I can't say I disagree).
>
> So the only real benefit of a block-level CRC would be to guard against
> bits dropped in transit from the disk surface to someplace else, ie,
> during read or during a "cp -r" type copy of the database to another
> location. That's not a totally negligible risk, but is it worth the
> overhead of updating and checking block CRCs? Seems dubious at best.
Agreed.
-- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610)
853-3000+ If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill,
Pennsylvania19026
