Subject: Re: UBC status
To: None <>
From: Matt Thomas <>
List: tech-kern
Date: 09/27/1999 10:13:42
At 09:54 AM 9/27/99 , Thor Lancelot Simon wrote:

>How, by waiting for all the previous writes to complete, at the drive's
>leisure?  Even that seems prone to failure: if you look at the Linux 
>BusLogic driver you'll find a comment about issuing an ordered tag every 30
>seconds because the author had encountered drives which *never* wrote some
>simple tags otherwise (it's been suggested to me that this isn't legal 
>default behaviour, but might be triggered by certain mode page settings on 
>some popular drives).

FWIW, the DEC RZ25L had a problem with tags such if enough I/O happened,
some tagged requests would be seriously delayed.  The drive was trying
to optimize access and travel and if a I/O went to an idle part of the
disk, it might never get serviced.  Digital eventually released an 
update for the firmware to correct this problem.
Matt Thomas               Internet:
3am Software Foundry      WWW URL:
Cupertino, CA             Disclaimer: I avow all knowledge of this message