From owner-freebsd-hackers Wed Apr 16 14:08:46 1997 Return-Path: Received: (from root@localhost) by freefall.freebsd.org (8.8.5/8.8.5) id OAA07514 for hackers-outgoing; Wed, 16 Apr 1997 14:08:46 -0700 (PDT) Received: from lariat.lariat.org ([129.72.251.2]) by freefall.freebsd.org (8.8.5/8.8.5) with ESMTP id OAA07438; Wed, 16 Apr 1997 14:08:35 -0700 (PDT) Received: from solo.lariat.org ([129.72.251.10]) by lariat.lariat.org (8.8.5/8.8.5) with SMTP id PAA05793; Wed, 16 Apr 1997 15:07:49 -0600 (MDT) Message-Id: <3.0.32.19970416150727.006ccadc@lariat.org> X-Sender: brett@lariat.org X-Mailer: Windows Eudora Pro Version 3.0 (32) Date: Wed, 16 Apr 1997 15:07:36 -0600 To: pete@sms.fi, kallio@cc.jyu.fi From: Brett Glass Subject: Re: Repeated UNIT ATTENTION, what is it, is this serious? Cc: hardware@FreeBSD.ORG, hackers@FreeBSD.ORG Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Sender: owner-hackers@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk In SCSI-speak, a "unit attention" condition means that a device was reset, was powered up, or had a serious error. The host is notified of the condition not when it occurs but only when it tries to send a command to the device -- which might be quite some time later. The command is rejected, but usually succeeds when it's retried. This is a hack that was added to SCSI because there was no easy way for a peripheral to notify the host right away when an error occurred. The problem could be anything from a parity error to overlapping SCSI IDs to bad termination to soft errors on the disk or tape. --Brett