Re: Driver retries disk errors.

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

On Llu, 2004-08-30 at 19:26, James Courtier-Dutton wrote:
> Theodore Ts'o wrote:
> > If the block gets successfully read after 2 or 3 tries, it might be a
> > good idea for the kernel to automatically do a forced rewrite of the
> > block, which should cause the disk to do its own disk block
> > sparing/reassignment.  

Not really as far as I can tell. It isn't a disk any more, its a storage
appliance on a funny connector. It already knows a lot about retries
internally as well as rewriting blocks with high ECC error
count. In fact you actually have to issue a different command to do 
read/write without retry.

> It does the same retries with CD-ROM and DVDs, and if the retries fail, 
> it disables DMA! It even does the retries when reading CD-Audio.
> Maybe there should be a "retrys" setting that can be set by hdparm, then 
> we could set the retry counts, and what happens when a retry fails on a 
> per device basis.

It probably should be smarter about error strategy here. You can use
hdparm to control some of this in the IDE case but not enough.

Alan