[illumos-Developer] Changing sd_io_time to 8?

[Albert Lee]

On Fri, Apr 29, 2011 at 4:26 PM, Richard Elling
<richard.elling at richardelling.com> wrote:
> I'd like to change sd_io_time from 60 (!) to 8.
>
> For those who are unfamiliar, sd_io_time is the default time before the sd driver
> will timeout a command. By default, it will retry 3 or 5 times before failing the I/O.
>
> From http://src.illumos.org/source/xref/illumos-gate/usr/src/uts/common/sys/scsi/targets/sddef.h#1704
>
>    /*
>    * 60 seconds is a *very* reasonable amount of time for most slow CD
>    * operations.
>    */
>    #define     SD_IO_TIME                      60
>
> Many RAID cards give up at around 8 seconds. Many HDDs guarantee some sort of response
> in under 8 seconds (enterprise or RAID version).  If a consumer-grade drive can't get it's act
> together in 8 seconds, not much chance it will get any better in 60 seconds. Nobody cares about
> 1x SCSI CD-ROMS circa 1989, except perhaps the SPARC folks :-)
>
> Thoughts?
>  -- richard

This tunable should probably become per-device. I'm concerned because
of the recent fiasco with consumer-grade disks.
http://en.wikipedia.org/wiki/Time-Limited_Error_Recovery lists
timeouts for some other controllers and implementations.

-Albert