"Pamela" wrote in message
...
On 12:09 19 Jun 2019, T i m wrote:

On Wed, 19 Jun 2019 11:15:30 +0100, "dennis@home"
wrote:

On 19/06/2019 09:04, T i m wrote:
On Wed, 19 Jun 2019 13:15:40 +1000, "Rod Speed"
wrote:

snip

You're thinking of the Red Book specification for CDs and DVDs

No I am not. I am thinking about the hard drive retrying writing
a sector when it doesn’t initially succeed in writing a sector.

Let's see if we can think up a technical name for that so everyone
knows what we are talking about ... how about 'Read after write
verification and / or 'Bad block remapping'?

HDD don't do read after write verification.

Some HDD's can / do (SCSI etc).

Tape drives do by having two heads.

shrug



And are you sure it's always done in the drive, not also by the OS?


Bad block mapping can be done by the drive and/or the OS.

Once that block has been considered bad by RAW.

The question is whether a PVR uses blocks
of bad data at all, in the way audio CDs can.

Nope, what matters is what happens when a write fails.

Unless the microcode on the device had been re-written, I expect
corrupt data blocks either get parity corrected within the hard
drive or else get flagged to the PVR's OS as an unusable block.

That’s reading, not writing.

Much as a PVR might manage to replay a corrupt video stream, I'm not clear
if
it would be permitted.

Of course it is.