Re: ASC/ASCQ Review

On Thu, Jul 13, 2023 at 12:14 PM Warner Losh <imp@bsdimp.com> wrote:
>
> Greetings,
>
> i've been looking closely at failed drives for $WORK lately. I've noticed that a lot of errors that kinda sound like fatal errors have SS_RDEF set on them.
>
> What's the process for evaluating whether those error codes are worth retrying. There are several errors that we seem to be seeing (preliminary read of the data) before the drive gives up the ghost altogether. For those cases, I'd like to post more specific lists. Should I do that here?
>
> Independent of that, I may want to have a more aggressive 'fail fast' policy than is appropriate for my work load (we have a lot of data that's a copy of a copy of a copy, so if we lose it, we don't care: we'll just delete any files we can't read and get on with life, though I know others will have a more conservative attitude towards data that might be precious and unique). I can set the number of retries lower, I can do some other hacks for disks that tell the disk to fail faster, but I think part of the solution is going to have to be failing for some sense-code/ASC/ASCQ tuples that we don't want to fail in upstream or the general case. I was thinking of identifying those and creating a 'global quirk table' that gets applied after the drive-specific quirk table that would let $WORK override the defaults, while letting others keep the current behavior. IMHO, it would be better to have these separate rather than in the global data for tracking upstream...
>
> Is that clear, or should I give concrete examples?
>
> Comments?
>
> Warner

Basically, you want to change the retry counts for certain ASC/ASCQ
codes only, on a site-by-site basis?  That sounds reasonable.  Would
it be configurable at runtime or only at build time?

Also, I've been thinking lately that it would be real nice if READ
UNRECOVERABLE could be translated to EINTEGRITY instead of EIO.  That
would let consumers know that retries are pointless, but that the data
is probably healable.