Re: ASC/ASCQ Review

On Fri, Jul 14, 2023, 11:12 AM Alan Somers <asomers@freebsd.org> wrote:

> 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?
>

I'd like to change the default actions. But maybe we just do that for
everyone and assume modern drives...

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.
>

Unlikely, unless you've tuned things to not try for long at recovery...

But regardless... do you have a concrete example of a use case? There's a
number of places that map any error to EIO. And I'd like a use case before
we expand the errors the lower layers return...

Warner

>